Here's my opinion (Might be false)
Last year - 2020
York Resources (Amazfit Band 5) ;- Doesn't have Xiao AI images which give a hint that York won't be on Mi Band 5. And turns out to be on Amazfit.
Kongming/Pro Resources (Mi Band 5) ;- Doesn't have Alexa images but has Xiao AI which most likely mean Kongming/Pro will be in Mi Band 5 and not on Amazfit.
This year - 2021
Pangu Resources (Mi Band 6) ;- Both of them has Xiao AI and Alexa images, they most likely will be published in the same company and it's probably will be in Xiaomi.
This make's more sense. If the resources doesn't has Xiao AI in it. It has less chance to publish on Xiaomi but more chance to publish as a Amazfit. Since Xiaomi mostly use Xiao AI on their Mi Bands.
Double checking -
On York Resources, Start from Images 0000 - 0059 is Alexa images. This is true that Alexa will be available if they images is most likely on the first 0000 to 0059 (Might be change to later Ver)
While Xiao Ai most likely on the bottom images. I feel like they taken York version and reedit it and place Xiao AI on it. This is fine, they just need to rescript it for both of them to work. They mostly using York because York has already capable to use SpO2. Amazfit Band 5 might be the test for early SpO2. And it seems successful and they seems to use the SpO2 for newest Mi Band 6. This is might be the reason why they use Amazfit Band 5 to run SpO2 and Alexa. Maybe they wanted to check if it's capable of doing it before using it on official Mi Band. Who knows?
Sorry for such a long Essay. LOL :V