A laudatory to one's teacher is a sine qua non, but the tradition has held on that way. Ramanuja takes a minor digression from this during his gloss on Gita. Barring this, the school does not show such jumps, so to speak.
Given the above, the text that quotes S.Mishra's as a student of Srivatsanka is subject to doubts. For more reasons than one, this holds true. First, as the above goes, the lack of general practice in this direction.
Second, borrows from Bhatta Parashara of approximately the same time. Bhatta uses govindatAtau in his opening lines for his father and his teacher. S.Mishra attributes a single verse to Ramanuja and continues with his work in contrast. With no mention of Srivatsanka or any other, it furthers the invalidity of the connection.
The third is the fact that this is a non-extant textual variant that has no corroborations. No other version in vogue, of AMM's commentary to PLC's MMP, hold this statement where AMM quotes S.Mishra.
What shows up in all, is how the school Ramanuja restructured remained fluid. Both sides quote each other, and non-sectarian works like S.Mishra's, adding testament.