Command Block Question

[spiral junco]

@s selects the entity executing the command. In a command block, no entity is targeted by default, rather the command is ran by the block. Buttons, levers, and any other redstone contraption simply provide power to the command block.

So no, a button will not set the player as the target for @s, you would need to select them first with something like @p, which can have issues targeting the intended player sometimes.