"Is not at all unheard of for a SFH that was worth max 500K on the SFH market to be bought for over a million by developers when an area has gotten upzoned."

Yes, but that's only for holdouts, which is a game of chicken. And after the developers build around you, you're done, your home value plunges as you're surrounded by traffic and apartments.

"Now, going back to jobs, in practicality, allowing upzones, also tends to bring way more jobs - more coffee shops / corporate towers etc."

The two are unrelated. Cities have a lot of exclusive-use commercial or residential areas. You can increase the same jobs without having more residents, which increases value for the home-owners.

Which is exactly what is happening in the US.