Yes, as a violinist (/teacher) I avoid "barre"-like fingerings that use the same finger in the same spot on an adjoining string under a slur. There are times that we're forced to do this, but it's not fun and you can be more lyrical by using a different finger. The problem is that you have only two options:
- To "center" the finger as you normally would with the pad of the finger centered on D string, and then "move" the finger to the A string, sliding sideways. If we weren't under a slur that could be done by lifting the finger (or at least lightening its pressure) and moving. But under a slur, it would mean dragging the D string sideways, "snapping" off of it onto A—not a pretty option. (If we were absolutely forced to take this course, it would be reasonable to briefly interrupt the bow's slur while moving; this quasi-portato is often appropriate especially in Tchaikovsky's hyper-expressive mode; Kreisler does it all the time.) OR
- You could, anticipating the string change, plant the finger equally centered on both D and A strings. The problem here is, on a fretless instrument, it's hard to get the string to securely and firmly contact the fingerboard on both strings, especially if you're adding vibrato. Intonation for both pitches will be challenged. And, should one have no other choice but to do this, for heaven's sake please not with the 4th, the narrowest finger!
So yeah, I frequently choose fingerings that switch strings while also changing finger. That said, I find the fingering of the previous notes odd. Is the first slur immediately after the Tempo 1 in second position? Ideally it would be nice to arrange the fingering so as not to even have to cross a string during a slur. Maybe the assumption is you start in first position, change to second on the A to avoid an open string, change to third on the F that is the subject of this question so as to avoid "sliding" or "barring" a finger, and then presumably extend the first finger down into second position on the C. I'm guessing the goal here is to have a very clean sound, free of the audible slides of shifting, or else the fingering might have just stayed in first and shifted up to the F audibly.