Interesting question...your friend may be on to something. I've never seen any info on this subject as it relates to trailers, but heat buildup due to poor wheel well air circulation is evidently known to be a problem with dual/rear wheels on buses (and motorhomes?).
Here quoting from
this Tire business.com link Tire Business wrote:
The rear tires of transit buses and motor coaches are especially vulnerable to high temperatures due to the lack of air flow around the tires.
It's probably important to note that according to that author, circulation evidently only becomes a problem when some other malfunction (underinflation/bad bearings/etc) begins to generate extra heat. He doesn't say how/if tire temps are affected by wheel well airflow during "normal" operation.