This feels to me like a ford/chevy opinion poll.
You're exactly right. There are people that have pulled in CAT cable with a CMR jacket into conduit 10-15 years ago without an issue. We only hear the GOOD reports of such a practice. You likely won't hear of the BAD reports.
Water gets into underground conduit, mostly because the conduit at some point comes up and into above ground boxes, etc. and
*Thermal Differential Cycling provides a means to pull moisture in but not to let it out.
My point?.....Use flooded burial or direct burial wire even inside of underground conduit IF you install conduit for protecting against gardening, gophers and shovels otherwise just go with the same direct burial / flooded burial conductor right into the ground with NO conduit. Personally, I would not waste my time pulling a CAT cable with only a CMR, CMP or CMX jacket into underground conduit...just be prepared for the stories from those that have had success doing so.
The HDPE jacket of a cable rated for direct or flooded burial is also more resistant to slits, cuts and abrasions from sand, grit and rocks in PVC and metallic conduit slivers that may work their way in during installation or pulling..
* Thermal Differential Cycling : the device heats up during day, air inside expands, cools off at night and contracts, drawing in damp outside air, condenses, travels to low point, is trapped and won't escape during warm up cycle, just continues to collect inside at low points.
-TonyR 2020