Level Up (A5E) Why is stunning strike not a (re)action?

[tetrasodium]

A (newer) player recently said how they'd like to make their cantrip spell attack into guiding bolt before they decide if they want to burn the spell slot citing the adept stunning strike herald's smite & various maneuvers using the same "and I'm going to make that into [guiding bolt]" phrasing regularly used near them around the table".

At the time I laughed it off & said no but looking into it made me start wondering. While smite is per long rest like the player's spell slots & most maneuvers are an action or reaction. The maneuvers are almost all an action or reaction & smite is a per long rest ability but adepts can stunning strike by spending 1 exertion at no action cost after seeing if one of their multiple damage dealing attacks land & get that exertion back by spending hit dice or just spending nothing but a short rest making it seem like that player's "why not, what if it was hold person instead of guiding bolt?" question put stunning strike in a questionable position.

Does stunning strike do the stun instead of the damage that attack would have otherwise done? Is stunning strike not costing anything in the action economy an oversight?

 

[W'rkncacnter]

stunning strike stuns on top of damage (because, like smite, it procs on a hit). it should be noted that, at higher levels, a lot of monsters have very high con saves, so it arguably falls off in usefulness as a result.

also remember that brute fighters can spend exertion to deal extra 1d8 damage at a 1-to-1 rate up to their prof bonus per turn (i.e. up to 6d8 at level 17+), meaning a herald x/brute fighter 3 basically gets o5e smiting back except far more often due to the more efficient exchange rate of herald spell slots to exertion...oh, and that stunning assault (i.e. 2 exertion, make all your attacks, all counting as a stunning strike - including any opportunity attacks you hit with until the start of your next turn) is a thing that exists. i'd say stunning strike is far from the strangest or most broken exertion ability in a5e.