I don't know why they would have a tach, they are not really used now, and if you did need tach operation, the Hall sensors would do it as a digital tach.
It looks like they have the latest type of encoder that also has commutation tracks on it that simulate the old hall effect devices once used.
Re-reading the description it points to the motors being 3 phase synchronous rather than BLDC? The former generally uses a different commutation method than BLDC.
??
Al.