It should also be pointed out that we have definite proof of non-Dynamis limit breaks from the Ktitsis Hyperborea Trusts. Those three can't use dynamis and yet can crack out LBs, although I believe their AI isn't tremendously inclined to. And I'd find it hard to believe the Machinist LB3 is anything but exactly what it looks like.

So basically, 'dynamis LBs' are a pretty cool idea that works sometimes, but also there's definitely instances were someone just... makes a giant fireball once in a while. So if you're a roleplayer trying to write up your own LB you can go either way and have decent grounding.