I personally think its neat that they are diving even more into ecology for mon inspiration. Gen 7 played with that concept a fair bit through regional variants being introduced, dex entries mentioning how the Pokémon Wildlife work and lots of places having worldbuilding text about how the location works with the Pokémon that inhabit it. (Also fwiw Alolan Diglett are not found near water, they're still cave encounters mostly)
This is something about the teaser that I think is being overlooked - SV will have a lot of interactions between the Pokémon and their ecosystem. The teaser shows Sandile and Krokorok swimming through sand, Psyduck going for a swim (keeping PLA's situational animations), Zangoose and Seviper hissing at one another, a lot of that stuff. I went over some speculation in a previous post of mine how a lot of text descriptions we have for the mons so far mention how they act in relation to one another (Wooper poisoning mons near itself, Grafaiai paralyzing bugs, Lechonk driving bugs away, Cetitan in a vid scaring Cubchoo). To me, today's teaser reinforces that the overworld in SV sill be much more dynamic than we've seen in SwSh or PLA
If anything I think Diglett is just kind of a weird choice for the first mon to do this concept with because its already super simplistic so they can't do much with it to really solidify the idea. Maybe we will have more convergent species in the future that do more with the idea, cause imo its a fun idea to explore with other mons