espinales, selvas, pastizales, estepas

As of right now, PB's most significant contribution to the episode 4 climax (other than rolling out of the way of the doctor's shot) is allowing you to run to the morgue and pick up the fireaxe. However, as far as I'm aware, this accomplishes absolutely nothing other than some flavour text and getting to annoy either Reese or Wayne when they're fighting each other (which doesn't seem to impact your relationships either way). If you don't attack either of them, the axe will be dropped to the ground or straight up forgotten when Reese is about to attack his mother.

So this axe probably has something to do with whatever tony is talking about here. But what would it allow you to do? There's some options.

Killing/wounding Wayne? This is the least likely one in my eyes. Wayne is a little too important to the overall narrative to just be able to die midway through. Also even if you were able to fend him off successfully when he's fighting Reese, there's still the issue of Reese wanting to kill Doctor Kelly. Getting rid of the roadblock that is Wayne by no means would count as an "extra episode 4 ending".

Killing Reese? This is regrettably a lot more likely than the last one. Since Reese is already able to die by Tabitha's hand. However, I would not describe using an axe to kill Reese as "one last hurrah before the game's finale." Burning Reese is already depressing for everyone involved except Tabitha, so getting another way to accomplish it just wouldn't be it.

Fighting back against Reese? This is the one I want most but let me explain:

Imagine you get the axe but decide to keep it until you're next to Doctor Kelly. She tells you to give her the tranquilizers as Reese is fast approaching. But instead of sedating him or letting her die, you fight back against Reese (who's already wounded from fighting Wayne). Eventually you're able to fend him off (not killing him) and he runs away. This way, everyone survives but nothing is really resolved otherwise.

Doctor Kelly still thinks her son is a threat to the world at large, not even getting to see him pacified by a Hot MC. She could still take a liking to you in Episode 5 since you defended her but she's still severely worried for what Reese could do.

On the other hand, Reese absolutely despises you from this point on, on a similar level to how he acts in Episode 5 status quo except he's free. He may or may not plan to do something else in the future to either you and his mom since you have taken her side so fiercely. You also can't romance him this way (still needing either the Hot trait or for Doctor Kelly to die for that to happen).

These downsides keep it from being as satisfying and consequence-free as the Hot trait save. It would make it similar to Tabitha sacrificing years of her life in Episode 3. It's an ending that has special requirements (here it's a trait, and in Ep3 it's a good relationship with her) and unique consequences (here it's Reese hating you, and in Ep3 it's Tabitha cutting her life short for sins she didn't commit).

This goes without saying that you wouldn't be able to do this if you're old (too much to bear) or if you called Tabitha beforehand (she would simply interrupt the fight with her gun before it can happen).