Photos not downloading from iPhone to MacBookAir

The photos from my husband's iPhone are not downloading to our MacBookAir (MacOS11.6 version).

Our MacBookAir is registered to my AppleID. I'm able to download photos directly from my iPhone to it via a USB cable.

The same cannot be said for my husband's iPhone. He has his own AppleID. When I try to download his photos directly to the MacBookAir via a USB cable, the photo count is not the same. MacBookAir recognizes ~9,000 photos when he has 17,000+ photos, the new photos recognized count is incorrect, and it does not recognize all the albums he created. We have plenty of storage on the phones, cloud, and on the MacBookAir, and bandwidth/WiFi is not a problem. We have tried several times over the span of several months with the same result.

Is there a way to add my husband's phone and/or his AppleID to the MacBookAir account or add him as a user or add in some way so we can add all of his photos to a hard drive photo library? I'm the primary user of the MacBookAir and he does everything he needs to do via his phone, so it's more about just backing up his photos on a hard drive in addition to the backup on the cloud. We have no problem with sharing the MacBookAir for our photos.

Basically I'm looking for the simplest way possible to add his photos to the MacBookAir hard drive and keep them updated regularly. I'd prefer to add them from his phone via a USB cable rather than futz around with downloading them from the cloud. Appreciate any advice!