If you run DATE /T and %DATE% on 100 systems running CMD, you'll get about 99 different answers, because it's dependent on your locale and how you've defined your date/time display. So there isn't really any concept of "compatibility" here, because CMD on one system will not be compatible with CMD on another. (Or even on the same system if you write a batch file and then alter any of the defaults.)
The only difference between TCC and CMD in the DATE /T output is that CMD puts a leading 0 on the month, which doesn't seem either particularly readable or useful. CMD puts a leading (language-specific) day of the week on the %date% format (and a leading 0 on the month), which also doesn't seem especially useful.
Why do you think emulating the CMD behavior (and breaking existing TCC behavior) is important?