They managed to make Colosssus Slayer passive with parameters, so Sneak Attack should be possible too. Making it a mainhand action only nerfs the Rogue by reducing the effective accuracy of Sneak Attack.
Rogues have gotten the short end of the schtick in BG3 in general. Where is their Expertise feature? It is really important.
Well, now when you mention it ...
Shouldnt that also be toggable? I mean you loose quite huge tactical advantage, if your valuable resource is consumed for first attack that meets the conditions. :-/