Comment by staticman2

The question is based on a misconception. Here's what my particular camera can do, the Fujifilm X-T5, from dpreview.com:

"Fujifilm says the camera can shoot 6.2K/30 video for 90 minutes or 4K/60p for 60 minutes at 25°C (77°F); these numbers drop significantly at higher temperatures, and there's no option to add a fan to compensate."

Here's what the next more expensive, slightly bigger camera can do the Fujifilm X-h2, from Cameralabs.com

"Also inherited from the X-H2S is unlimited internal recording, sailing past the previous half hour limit and also without overheating issues in my tests. I made five separate recordings, each starting with a full battery, and was able to record between 100 and 120 minutes in any format from 1080 to 8k before the battery expired. In each case at the end of the recording, the camera had become very warm behind the screen, but showed no warning of overheating. Battery power was the limiting factor in these tests.

All my tests were made at room temperature in the UK, but if you’re filming under hotter conditions and experiencing overheating, you can extend your recording times by fitting an optional fan accessory. As seen here on the S version, this simply screws into the back of the body when the screen’s folded out – not particularly elegant, but it will extend your times."

It seems to me it's clearly an issue of heat management in a small form factor since an optional fan accessory extends the film length in the higher end camera.