There are reports of BMW doing this as well. However, their customers receive a DETAILED build report, knowing in advance what their car does and does not have as well as re-imbursement if they couldn't follow-through on their end.
I don't think it has anything to do with Elon or business vs engineering. If I was coming to your place and said I was bringing pizza but I show up without it, you're not going to like it. Now imagine if you paid for the pizza...
Also I don't think Elon is out here making these low-level decisions, he's trying to take Tesla world-wide, get Space-X, Boring company, Starlink etc. going. Probably somebody else internally thought this was a brilliant idea and nobody would notice.