Remathilis
Legend
Take high elf and compare it to AE or eladrin.Can you explain what you mean by this? How is it a trap? It appears to be the most flexible of the three elf subspecies.
Obviously, no one will have the evidence you want. But why would you expect them to build off a setting-specific book rather than the more substantial (and thoughtful) MotM?
First, we cancel out dark vision and fey ancestry, because all of them get those so no comparison. Let's look at what's left.
Trance in MotM/AAG gives bonus proficiencies that are swappable on long rest. MotM gives two tools/weapons, while AAG gives one tool/weapon and one skill. That is HUGE. Need someone who can navigate a ship? Elf. Need someone who can make healing potions during downtime? Elf. Found a +1 halberd no one wants? The elf wizard can use it starting tomorrow. The high elf? Nope. Just what your class and background give. Advantage MotM.
Keen Senses gives the MotM elves one skill (vs the PHB a choice from three) but that skill is the GOAT skill anyway. Insight and survival are lacking compared to Perception, and the only reason you would pick them is that you got perception from another source already. Slight advantage PHB, but 99% of the time, it's even.
Both eladrin and astral elves can teleport 30 ft as a bonus action prof bonus/day.. This teleport is not a spell, so the prohibition on bonus action spells and action spells does not apply. An eladrin can fey step and then cast fireball while casting misty step would limit them to a cantrip. Further, 2 a day scales to 6/day and starts at level 1. A high elf gets misty step once per day, at 5th level. Want to teleport again? Use a 2nd level or higher spell slot. Advantage MotM so much it isn't funny.
So what does that leave? Well, astral elves get a cantrip from a small pool of light-themed choices. Sacred flame isn't the best cantrip, but it's free. High elf gets one cantrip of their choice from the wizard list, changeable on a long rest. Arguably better if only for larger options. Advantage PHB. The eladrin don't get a cantrip, but do get riders on their fey steps that can charm, fear, damage or carry others starting at third. It's power is of course limited to the number of times they can teleport per day, and they an only use one effect until they rest. The high elf gets detect magic at third, a spell that any full caster worth their salt has as a ritual and rarely is the 10 min casting time a deterrent. I guess it's nice that as a free prep you don't need to use a slot to prepare it anymore, assuming you're not a wizard or a book of shadows warlock.
So is your choice of a wizard cantrip and detect magic and misty step 1/day worth two free proficiencies, multiple non-spell teleports per day, and either teleport riders or a limited cantrip choice? I don't think it is. And anyone with a single optimizer bone in their body is gonna see that. High elf is a trap for anyone who has access to MotM or AAG.