@Seaberriesask your husband if he has aphantasia. Ill explain what it is in a minute. I was in my 50s before I found out I had it.
If there is no trauma in childhood this is the only other explanation I know of.
I do have trauma in childhood, and I'm on the spectrum so that makes it more common.
However you don't need to be on the spectrum to have aphantasia. Link to it is below.
Aphantasia is to experience reduced, fragmented, or, no visual memory recall of their childhood.
Aphantasia is the inability to create mental images, often resulting in a "fact-based" memory system, where individuals know what happened but cannot "re-experience" or visualize scenes, leading to fewer, less vivid autobiographical memories. My memory is built by a filing system, narative
It is certainly what I have. It's little known, however about 3% of the population here in The U.K have it. Most don't actually know there is a different way of remembering.
I am very factual. I have a razor sharp memory, storing memories as concepts.
For example. I can't shut my eyes and conjur up a picture of my adult children, grandchildren, family anyone, anything. It's simply black/grey. Hence now I understand why my home is covered in family photos.
I think in words. I talk things out and need a narrative. If the narrative gets disruptive I need to rewrite it out to make sense of..
I can't just rejig film/photos in my head. Though I do know who people are etc when I see them. It's hard to explain to someone who doesn't have it.
It maybe that, however I hope this is useful for you or anyone else reading.
I know my mind has learnt to overcompensate for no mental imagery by having an extremely strong spoken linear narrative though no visual pictures
https://www.bps.org.uk/research-digest/people-no-minds-eye-have-less-vivid-and-detailed-memorie