I think you're lucky he wants to 'help' but the wording would annoy me, too.
DP generally does things without complaint (albeit with some encouragement needed sometimes - but I can handle that so long as it gets done) but 17yo DSS always thinks he's doing things 'for us'.
Like he'll shout me to tell me 'your washing has finished' (it's always actually more HIS washing than anyone else's as he changes his clothes about 500 times a day, and he could transfer it to the drier instead of shouting me), or this morning he announced he'd emptied the bin for me, and he'd put the dishes away for me. Both of which after I'd asking to, he then confirmed he'd done it 'for me'.
I just feel that at 17 he's not a child, and should be taking on some responsibility for the house he lives in. So no, it's not 'for me' - it's just what adults need to do in a family home! I don't think he realises his attitude is so bad sometimes, as jf I'm the sodding maid and every tiny thing he does (usually prompted) is relieving this massive burden I would otherwise have carried. No! If he notices the bin is full, the dishes need putting away, the washing machine has finished, it's JUST as much his responsibility - living in the house - as it would be me or his dad's. Yet for some reason when he does it he expects a fanfare.
I should start listing every single thing I do. I can't even imagine what he would say if I told him I'd hoovering the living room 'for him' even though that job benefits him just as much as him putting dishes away benefits me .. iyswim.