There is another reason why (especially cheap/"normal") thermal cameras have low frame rates. Basically higher (than 9!) fps cameras can be restricted for export and travel under ITAR (International Traffic in Arms Regulations).
Edit: also according to the specs it’s 160x120@9fps
https://www.dji.com/mobile/mavic-2-enterprise
640x480 isn’t native sensor size.
But yeah it must be that it is a non US company. Puts into question the utility of this ban. These mavics (all models, and not only mavics) fly in huge quantities over the front line in Ukraine.