Cap'n Kobold
Hero
Being RAW in response to a question about RAW is part of his job. The question posed wasn't about how he would rule it. It was a question about rules interaction so he answered it as RAW.I think Crawford is on the Spectrum. (I don't mean that as an insult, but as an explanation. A lot of us here probably are.) He has a great grasp of rules minutia, but sometimes he's WAY too RAW for my tastes. Here he answers a vaguely worded rule with a vaguely worded ruling! (Kinda explains how the rules get written so vaguely in the first place.)
And . . . I would really suggest avoiding discussing whether or not someone might suffer from any particular mental disorder here. Whether a fellow poster or not.
Arcane archer is a tradition that may have started with the elves, but has spread to other races: Ruleswise it is unrestricted in who can learn it.Arcane Archer is an explicitly ‘elven method’ that other races can learn as well.
Likewise, Bladesinger could easily be an explicitly ‘elven tradition’ that other races can learn as well.
Bladesinger is an elven tradition that is kept as a racial secret: Ruleswise only elves can be that subclass.
Thus bladesinger requires DM houseruling to be of interest to more than a small subset (people who want to be that particular style of gish) of a small subset (people who want to play en elf.)
XGtE is intended to have a much broader appeal, and anyone who really wants to play a bladesinger can probably access a copy of SCAG anyway.