@HamSBDad: In the recent past (about 2013), the NCAA “defined” an indoor track as 200 meters, but did not require that size for competition. Nevertheless, a particular conference might have their own rules which differ from NCAA rules.
P.S. I cannot find the requirement that you mention. Again, what is your source ?
The Millrose Games switched venues due to financial losses & the desire for a larger track, but not due to any requirement re: track size.