I wonder if magic tapped from a Waystone has the same property here that it does in 2E.
The/a reason for Miscasts is that the Winds are volatile, that they blow variably so a caster can lose their grasp of the magic as their strength fluctuates.
Magic tapped from a Waystone, by contrast is stable and predictable.
The way this is represented is that more powerful casters can draw on more magic (an number of dice up to their magic score, IIRC), but the more magic they draw on, the more likely they are of rolling a double, and so miscasting.
When using the Tap lesser magic to draw in magic from a Waystone when casting a spell ritually or performing a big R ritual, the extra magic from that doesn't increase the risk of causing a Miscast that using more magic usually does.
The Tap lesser magic's main purpose isn't just to get more magic, it's to get safer magic.