I have no idea...

I'm a had the impression that it's like that stun move from Fate/EXTELLA, whereby it stuns anyone in a straight path. ( っ'-')╮・・・・・---------->

Which usually misses anyway...

It's not that the enemy evades, you miss :P

It is logical. You evade the DMG, not the stun.

If it ain't coded to work as such, it won't.

With Hakuno's "Ignore Solemn Defense and Invul BUT NOT Evade", I'm assuming we're bound to get "Special Stun" servant somewhere before the game closes?

But yes, technically it makes little to no sense

We are in a franchise where "so you dodged my unavoidable Spear", so it actually doesn't make sense in the beginning.

Other games has the evade not working when stunned but, not FGO. Fate works different I guess.