Where are you getting this from?
They use spells to fly, for one thing.
Olive's point is that there is much, much more to "fighting skill" than "flailing around with swords and fists and aerial dogfighting".
A rather good example would be Fate and Nanoha. Currently, Fate is still better at magic, but Nanoha is fast catching up, since her learning curve for spells is something just short of "utterly fucking hax".
However.
Nanoha may well be - and certainly will become, by the time they're adults - the better
spellcaster. Give them both a spell - almost any spell, barring ones that fall into their relevant specialities, like shooting magic or speed spells - and Nanoha can learn it faster, cast with more control and precision, and understand it more comprehensively. The breadth of spells she knows; her "library", will very soon outstrip Fate's, if indeed it hasn't already done so.
Fate can still beat her - not just beat her, but
kick her ass - about four times out of five in sparring matches.
Why is this? Because Fate is the better
fighter. Nanoha might have more spells, or fancier spells that are complicated and sophisticated and powerful. But there is a difference between "knowing how to cast a spell" and "knowing how to
use a spell in combat". There is a difference between "knowing fighting magic" and "
actually fighting".
Fate is very, very good at combat. Precia actually isn't sure whether this is due to Project Fate or just a natural trait stemming from some sort of cosmic joke, but despite having what I tend to call a "healer personality" - an empathetic, caring, nurturing outlook on the world which doesn't like to see people hurt, and tries to ease suffering where it's encountered - Fate just
gets combat, on a level that Nanoha simply doesn't. She has the instinct for it. She can read her opponent, she can think ahead, she knows
where and
when and
how to use her tools - be they scythe-blade or shooting spell or a freaking sushi bowl - to best effectiveness, or at least to
high effectiveness. She doesn't freeze, she doesn't often panic (at least not until after she's lost, like when Zafira caught her and she thought Alicia was dead), she doesn't stop in the middle of a fight to think "okay, now what's my next move?" or plan ahead too far. These skills, the skills one uses in
actual fighting; they're distinct from simply knowing a lot of spells that can be used to shoot someone. Handing someone a gun and showing them how to fire it does not make them a soldier. And while these skills; the skills pertaining to the
process of combat, can be taught, they still come a lot more naturally to some people than others.
They don't just apply to a one-on-one in-person fight, either. Look at the end of Game Theory. Fate and Nanoha were both put in charge of one aspect of the Garden's systems. Nanoha got the outer defences, tried a bunch of complex flashy stuff, got flustered, panicked, messed up and broke half the Garden. Fate got put in charge of the inner defences, set up a beautifully vicious trap network, used the tools she had in ways she knew would work, and quickly and efficiently took out almost everyone who managed to board the Garden. Linith saw this quite early on while she was training Fate. It's one of the reasons Precia so firmly decided to use Fate efficiently as a valuable asset. Nanoha is better at
magic, but Fate is the better
fighter, and it shows.
Precia, then, is even further down the line between them. She is very, very,
very good at magic indeed. But she's still not very good at fighting. And neither is she particularly good at military tactics and strategy - and yes, 00Zy99, that includes the kind of strategy that goes into contests of "I want to fight you on my terms, where I can just blast you from range", vs "we're going to foul up your operations and stop you from being able to do that, then box you into a corner so that you
have to fight us in person where we can murder you". You will notice that despite all of the defences she set the Garden up with, Zest and Quint still penetrated in to fight her, and it was only the fact that she was running off a Jewel Seed tap at wtf levels of power while the Garden fell apart around them that allowed her to survive that confrontation (and Zest still noted that she was flagging, and that if Fate hadn't arrived and cast several healing spells on her, she'd probably have collapsed in a few more minutes).
TL,DR: Using your tools and resources efficiently and on the fly to outmanoeuvre your opponent, force them into a confrontation they cannot win and then crush them, while they do the same to you and make things go horribly wrong with your plans,
is a form of fighting skill. It's called "tactics and strategy". Precia is good at planning, but when it comes to dedicated military tactics and assaults, she is not the biggest chick on the block.
After all, the biggest chick on the block would technically be Heidi, who is almost as tall as Zest.