I find the glue thing nice but my sceptic mind let me think that it could be another great trick to fight competition with generic battery manufacturers.
The glue goes with the battery, and there is probably a few patents on this magic glue, so generic battery manufacturers will be prevented to be able to add this glue to the new batteries they will want to sell.
In my experience, 3rd parties aren't worried about being identical to the original design. They'd just give you a square of double sided sticky tape to hold the battery down with, and accept that if you ever wanted to replace the battery again you'd have to destroy it to get it out.
The battery measurement software will never work again with any third party battery replacement. You will never know your actual battery value and the phone may shut off when there is plenty of juice available. Also Apple has software to detect if any part of the phone is replaced and will refuse repairs if any part is replaced. I was told this by the Best Buy authorized repairman as he spent 20 minutes checking my phone and I was told not to leave because they would refuse the repair if my phone had been touched!
I think vanishingly few parts you buy for iphones are clones these days - everything is stripped from dismantled phones.
Batteries being perhaps the only exception, and even then, the battery identification chip and flex cable is original apple, just the cell is switched out.
iFixit speculated that the tape is from Tesa. Tesa says it has filed "50+ patents for 'Debonding on Demand' adhesive tapes' … 'using various mechanisms such as temperature, electricity, laser and electromagnetic induction': https://www.tesa.com/en/about-tesa/press-insights/stories/de...
So generic battery manufacturers could presumably buy the tape from Tesa, license production themselves, risk producing their own variants, or supply replacements without electrical debonding (the consumer probably doesn't care that the replacement battery doesn't use the same debonding tech their original battery used).
The glue goes with the battery, and there is probably a few patents on this magic glue, so generic battery manufacturers will be prevented to be able to add this glue to the new batteries they will want to sell.