This sounds a little bit like the problem I had when I purchased a newly released Garmin head unit... the make and model wouldn't appear on the activity page.  I opened up a helpdesk ticket and this was their response: 

"Thank you for contacting Strava. Sorry the data from your device is not being recognized properly on Strava. We do not have this device mapped in our system yet - which can cause your activity statistics to appear differently from what you see on the original platform you use.

I've filed a ticket for our engineers to add this model to Strava. Thank you for your patience."

It took them two weeks to add it to their system, then the name started to show up. I think that's what you're going to have to do -- open up a new help ticket.

That being said, both parties (Strava & Amazfit) have to work together to match up the product code in the file created by the device with the appropriate code and device name stored in a lookup table on Strava’s servers.  If (like Wahoo) Amazfit doesn’t differentiate between generations of a device… you may be stuck with the current process.