Gilbert may have proposed that lunar craters were impact structures a long time ago (I'm tired of fighting with 20-minute page loads so I'm not going to search for it. I wish the crane operator hadn't smacked the aft satellite dish.), but that doesn't mean that his explanation was accepted at the time. As I said, the strong consensus at the time that Heinlein was writing (that book) was the lunar craters were volcanic phenomena. About 1962-63, an aspirant astronaut and field geologist, Eugene Shoemaker, started publishing and presenting papers arguing parallels between the structure of the small number of known terrestrial impact craters and the structures visible on the moon, and proposing that the large majority of the craters on the Moon were of an impact origin, not an eruptive origin. Through the 1960s Shoemaker argued the position, was ruled out of the astronaut corps for health reasons, and successfully changed the expectation until the Russian landers of the mid-60s shifted the balance of evidence appreciably in the favour of the impact origin hypothesis for craters.
Actually that's how science is meant to work. It wasn't as dramatic a paradigm change as the contemporaneous development and acceptance of plate tectonics and so was probably overshadowed in the popular press, but that is what went on.
Meanwhile, absolutely no-one has ever argued that all craters on the Moon are of impact origin and none of volcanic origin, in the same way that no-one has (TTBOMK, and I am actually a geologist) seriously argued that all terrestrial craters are of volcanic origin and none of impact origin. We know of craters and other structures on both bodies, of both origins.
Lunar rilles were proposed as possible lava tube collapses so long ago that I'd have to seriously look it up to find an alternative proposal (and that bloody crane operator!).
more recent papers on fairly RECENT volcanic flows (as early as 100 million years ago).
In the 1950s a variety of people (including the selenographer Patrick Moore, famous as a BBC astronomy broadcaster from the same period) were continuing to report "Transient Lunar Phenomena" from a number of places, and proposing that they might be the product of volcanic fumarole activity, or something similar. i.e. contemporaneous volcanic activity. Certainly not impossible, though it's not clear that Moore had really made his case. But he did present a good argument.
All that said, the overwhelming majority of the Moon's volcanic activity took place in the "maria-forming" period of about 4 gigayears ago (maybe as recently as 3.7 gigayears ago), and the structures formed then have only been lightly modified since. That is when the structures we recognise as "the Man in the Moon" were formed.
Check out volcanic glass recovered by Apollo 17
You seem to be under the misapprehension that volcanic glasses are of necessity "recent" (if not "Recent", or Holocene). This is incorrect. It is true that, under terrestrial conditions, volcanic glasses do devitrify fairly rapidly (I've sketched the thin sections ; I've actually used devitrification of (non-volcanic) glasses to estimate pressure-temperature conditions of a geological event as part of my mapping-derived Honours thesis. But I'll stress again that this is under terrestrial conditions. If you have a glass-forming melt which is very low in water, (and other volatiles, but principally water) then the devitrification rate goes through the floor as the mobility of ions in the glass drops considerably. By the time you're down to the millimolar (IIRC - marginal internet here, as I said above) water concentrations in your magma, it's perfectly possible to have glasses persist for billions of years. Your Apollo volcanic glasses could easily be Archean or Hadean in age (Before 2.5 gigayears ago, or 4.0 Gyr respectively : I've got Gradstein & Ogg's 2013 chart taped to the wall of the office.), and still be vitreous.
Heinlein's writing in the 1960s was based on the (incorrectly) accepted science of the 1950s. Which is actually quite up-to-date for a SF writer, and doesn't distract from the pleasure I get from reading the stories in the slightest. But people here do have a depressing tendency to get SF (and other F) confused with fact.