A dinger every 7.9 AB when the game was already pretty much decided. One every 18.7 when the score was within 4.
That's basically the difference between being a 30-HR guy if he ever got 600 AB, and a 40-HR guy. Not that 30 is bad, but combined with a low BA it ain't all that, either.
And when the game's not close, that 7.9 rate will fool us into thinking he's a 75-HR guy if we just give him the chance.
(And no, not every batter has splits of that magnitude. Byron Buxton had a good 2025, and when the game was within 4 runs he homered every 13.67 AB, while when the lead for either team was 5 or greater, his homer rate was every 16 AB - the opposite direction of Wallner. I'm not going to invest more time looking at other individuals, but across the majors those rates are 29.4 and 26.8 respectively - not especially different, one from the other.)
His ordinary splits with men on base look reasonable, but it could be that they're inflated by the meaningless situations. I don't know where to find further splits, of results with men on base versus bases empty, divided into the size of the lead when it happened. The one useful split b-r.com provides to go to this extra level, is what they term "late & close". In those very limited situations (and I don't know how they're defined), Wallner hit 1 HR in 33 AB, for a rather high ratio of, well, 33.
It's dangerous to slice and dice things into small samples, but if those small samples are congruent with what looks like an overall trend, I'm more inclined to consider them.
My working hypothesis is that Wallner is far more susceptible than most batters, to falling prey to the pitcher's strategy for the game situation. Which reduces his value far below what the raw numbers would suggest. I can't recall a player with such extreme splits in this regard - Joey Gallo maybe, although his unfavorable splits were of a different nature. I want, want, want the coaches to help Wallner figure this out.