Shalom Josh,

It's great to hear from you! While it is tempting to suggest that Tosfos is referring to different versions or editions of Rashi's interpretations when using the two different terms you mentioned, since I do not see any evidence of that off-hand, it is difficult to say what the specific reason for the discrepancy is, or whether there is a reason at all. But bl'n I will try to keep an eye out for any insights about this fascinating point you have raised.

Warmly,

Yishai Rasowsky