Only 1 out of 3 of these is true, and just barely true at that.
Since Varsho became an MLB regular in 2021 he's been a much better defender and baserunner than Kiermaier, and they are only a few percentage points away from each other with the bat.
From 2021-2023 Varsho received 1488 plate appearances, produced an overall offensive output of 97 WRC+, 9.2 total FWAR (3.4 FWAR/550 PA), 11.2 BsR (4.14 BsR/550 PA).
From 2021-2023 Kiermaier received 1041 plate appearances, produced an overall offensive output of 100 WRC+, 5.7 total FWAR (3.01 FWAR/550 PA) , 2.7 BsR (1.43 BsR/550 PA).
Varsho has handily outperformed Kiermaier defensively in center field, and it's actually not particularly close on a rate basis.
From 2021-2023 Varsho provided 21 DRS and 19 OAA in center field in 1019 innings. This equates to 20.6 DRS/1000 innings and 18.5 OAA/1000 innings.
From 2021-2023 Kiermaier provided 21 DRS and 25 OAA in center field in 2358 innings. This equates to 8.9 DRS/1000 innings and 10.6 OAA/1000 innings.
When comparing the two in relative value expected salary also needs to be factored in. I've seen estimates for Varsho to receive a $5.5 million arbitration based salary in 2024, vs Kiermaier who will likely be looking at a similar $9+ million salary for 2024. Moving forward Varsho is almost certainly going to be cheaper, provide more value in the field defensively, more value on the bases, close to the same value offensively, and be much likelier to remain healthy and available to play every day. By keeping Kiermaier the team would essentially be forcing Varsho to a corner outfield spot where he becomes far less valuable, and spending more money that would be far wiser to allocate to other needs vs rostering two elite center field defenders who need to be sheltered a bit vs top left handed pitching.