It has nothing to do with "could not legally buy one for themselves."
That is NOT part of the 'straw purchase' conditions.
No, but establishing that the buyer is not circumventing the background check process on behalf of a prohibited person is supposed to be the intent of the question. That is why I would love to see a well-prepared case similar to this come up in court before a decent judge.
An example that has happened: I bought my wife a shotgun for her birthday. We both went to the store, she filled out the 4473, passed the instant check and took possession of the gun, and I paid. The owner had just sold me a handgun a couple weeks before, and I did lay my CHL out with the cash in case he had any doubts. A picky prosecutor could say I had her straw purchase the gun so I could then give it to her, but that would clearly not fall within the intent of the question, particularly since she passed the check and I was exempt from it due to the CHL.
An example of the case I would like to see to establish precedent: Bubba Cruffler decides he wants to trade off one of his as-issued WWI 1911s for a WWII one, so he posts WTT, noting that he has a C&RFFL and will provide a copy on request. Charlie CHL a few counties away knows of a local shop with a great deal on just such a gun, so after establishing that Bubba is a good guy, he goes to the shop and buys the gun with full intent to immediately trade it off, then goes to meet Bubba, showing his DL and CHL before the trade as a similar good-faith proof that he can receive the WWI 1911. Bubba, of course, gives Charlie a signed copy of his C&RFFL and fills out his bound book with the disposition of the WWI and acquisition of the WWII, but as he's doing so, Adolf ATFGuy comes swooping in with the local SWAT team in a black helicopter to grab Bubba and Charlie for their evil(?) deeds.
Bubba, of course, likely had no knowledge that Charlie had just purchased the gun, and did his part by the book, so he should have a fairly easy time of it assuming no other problems are found with his bound book or collection, though getting either gun back will likely be a major hassle. Charlie, OTOH, violated the letter of the "actual buyer" question (and/or instructions) while making a well-documented good-faith effort to ensure that he was not violating its intent. A good outcome for Charlie would establish a precedent that would be helpful for all of us, and likely get the question reworded to more effectively reflect its intent.