I never quite understand complaints about “lack of progress” in series where the couple starts out together.
Sure, I get the desire to see more physical intimacy between characters, but in episodic stories about high school kids there’s a lot more comedic material to be generated keeping things fairly chaste than in ramping up the skinship or, as in this case, normalizing their public relationship.
“They’re dating but it’s a secret” is the whole founding premise—when that goes away, it’s likely that the whole series goes away (which may be where the presence of Abe-chin is pointing anyway).
Progress is essential to storytelling. There are more ways for a story to progress than "Girl meets girl. They become a couple. The end."
Personally, I find the "dating but it's a secret" framing device tiresome. We've never seen any evidence that any of their friends or family would react poorly to the idea of them dating. Their extreme caution to avoid even stuff that non-coupled female friends would do with each other seems at odds with how generally pleasant their world is. We get it, they're young and nervous but that is the area where they should be growing.
This is never going to be a story that deals with the reality of being gay in Japan - it's much more fantasy along the lines of the Kase-san series. So in that vein it would be nice to see them make strides in being comfortable with who they are and be able to enjoy each other's company more openly. Stories about lesbian couples don't have to only be about how they got together - straight couples certainly aren't limited to that. They can be a couple and deal with life around that and still have funny, relatable stories to participate in.
I actually really like this manga for the characters and the art style. I just wish the author would realize that they've outgrown the framing device and it's time to do more with the characters.