I don't think learners should worry about the appearance
of their fingers as long as they work for them in the way they're meant to.
I've seen kids with flat fingers, splayed-out fingers, 'excessively' curled fingers (not all at the same time), yet they play fine. A teacher who is wise will leave things well alone unless there are technical issues, tension issues etc. The priority is to ensure that they are playing correctly without unnecessary tension, rather than what they look like. Adult learners who notice visual 'oddities' on themselves start over-thinking, and when they try to 'correct' what they perceive as not kosher (probably based on watching YT videos of their piano idols) they just end up developing lots of tension and cramping their style.
FWIW, when I started learning piano, my non-playing fingers stuck out like rods. My teacher never corrected me. Within a few months, they started curving naturally as I developed finger control. (I'm basing it on photos my uncle took when I visited him and played duets with my cousins.) But what never changed were my pinkies, which always did 'collapse' at the middle (PIP) joints and bent at various angles at the distal joint when playing above mp. And they stuck out intermittently depending on what I was about to play. (BTW, I never noticed that until I made video recordings for a piano website a few years ago.) And none of my four teachers over the ten years I had lessons ever mentioned it, meaning that they never considered it to be a problem. I was a trusting kid when I was a student, and if my teachers were happy, so was I
What about now? Well, if anyone watching me play the piano (which is quite a number over the years I've been performing in public) thought my fingers look 'odd', they never mentioned it to me. Maybe because my playing was OK, despite the visual/cosmetic infelicities?