You need to recognize that the initial formulation of TMRS in relation to sheet film had some VERY precise applications in mind, especially with respect to precision matched color separations and accessory masks for use in dye transfer printing. Those requirements are more demanding on consistent negative development than what is needed for ordinary
black and white photography. They actually wanted to exceed the results formerly attained by Super-XX film in conjunction with HC-110. And that demanded that TMRS be used full strength at 75F in order to achieve the straightest characteristic curve possible. Apparently, ordinary TMax developer can't reliably withstand that without side effects.
In commercial labs dedicated to that color process, sheet film was conventionally developed in volume on hangers by hand, in replenished tanks. This was another key consideration. You need to look at it from that standpoint, not just the requirements of people like us. These were production lines, with particular individuals assigned to particular tasks - in this case developing lots and lots of sheet film in a very consistent manner. But there were also labs which standardized on their own preferred developers, less expensive than Kodak's new recommendation.