Videos in Photos library not all appearing in iMovie Media browser

Using iMovie on new M1 MacBook Air 16GB / 512GB under Big Sur 11.3. When I select all photos I eventually can scroll through all of my photos in my photos library. However when I select videos it only seems to be showing me like 32 videos - I have 4000 in my photos library. I can't seem to find them via any menu in iMovie?

Andy