Is there anywhere that specifically states how much longer an egg has to wait before it hatches? I feel like I've looked everywhere that one would expect to see this and I haven't found it. If it's really not a feature, it feels a bit silly... (This really applies to things like plants as well, I'm not sure why it's a mystery we have to find out in terms of what taking care of a plant entails.)

After reviewing the game guide for a third time I see that it's listed in the Pixdex once the egg already hatches, but why is that information that can't be known while one is still waiting for it?

I think the idea is that you're gathering data about these pets, so you wouldn't know the hatch time until you experienced it.

But if you'd like to know Pydeer's hatch time, I can send you a PM (so as not to spoil it for other people).

Could someone pm me the hatching time of Igupunk?

Not yet, that would be nice of you