Went and looked at data.
Over this month, Kirk called 14 games, Jansen called 14 games (not accounting for any late inning substitutions).
When Kirk called, overall ERA and FIP were 4.81 | 4.58 respectively. When Jansen called, overall ERA and FIP were 3.17 | 3.60.
This has a lot to do with Manoah/Bassitt calling their own games more than anything imo (or at least confounding enough for this to not have any merit).
But for just relief pitchers,
When Kirk called, ERA and FIP were 6.08 and 5.44 respectively.
When Jansen called on the other hand, ERA and FIP were 2.52 and 3.39 respectively.
There is a substantial difference.