Yeah, exactly. My mum used to buy shirts and underwear for my dad all the time, 'cause he's too lazy to do it himself, and no one ever twitched a muscle.
Besides that isn't it as much looked down upon as males buying female clothes (poor MtF's, seriously! :<). I bought a men's shorts a few days ago, my mum was there (I'm not out, but she approved, even though she kept steering me towards the more 'feminine' male stuff or pointing out 'nice' female things I 'really should try'), and I really felt like I was passing, UNTIL my mum started chatting with the lady working there, saying "Yeah, SHE will go to Rome next week. Ah, yes for HER graduation. I'm sure SHE'll have a great time." and I was inside the changing cabinet, feeling like I could sink to the floor RIGHT THERE. The lady who helped me still didn't say "Ehhh, those are men's" or "Are you sure? The women's are over there", etc. she might have looked a bit oddly, but I'm sure that was all in my head. (and she knew it was for me, as I tried it on in front of them, and my mum said I needed shorts 'cause it would be hot)
In other words; the people of the store don't CARE whether you're a (genetic) female buying men's stuff or visa versa, they just want you to BUY stuff, that's it. As long as they can sell things, they're happy.
And especially boring, non personal things, like underwear, socks (do SOCKS have a GENDER btw!?

Wtf!), shampoo, etc. are pretty common to be bought for someone else. (I was asked to bring a bottle of Axe for a friend some day, as well before identifying as trans, and no one gave me a weird look)