That's debatable. IIRC, Solar-produced tech is purely magitech (I could be wrong on that, but I think that's the case) which as has been noted, is limited in several respects compared to Tinker-tech. However, a Solar with Ability scores and Attributes of 5 can operate at double the normal human maximum level for invention/development from their Excellencies alone- and the right charms can boost that further. That's probably enough to put Solars quite a bit higher than a 2 on the Tinker rating.
Why didn't First Age Solars do this? I can think of three possible explanations (no idea which, if any, might be correct): Creation physics are different enough not to allow it, they were so used to working off a magitech basis it didn't occur to them, someone developed a low-essence charm to completely fuck over technology.