"from what I understand his heroin addiction contributed to him landing in Las Vegas"
I read that story, too, and always found it a bit incomplete... why didn't Chet Baker and Art Pepper end up in Las Vegas? Generally, most of the heroes of West Coast Jazz had a tough time recording small group jazz between the early 60s and mid 70s, Shorty Rogers, Russ Freeman all have similar gaps in their jazz discographies in that time (Shelly Manne would be one exception). And then stuff picked up again a bit, but on a smaller scale, Discovery became far more active again, there were some Japanese productions, some by Fresh Sound ... but indeed not much out of Las Vegas... the series on Woofy was later
https://www.discogs.com/label/789229-Las-Vegas-Late-Night-Sessions
there were some private productions out of Las Vegas but much fewer than Los Angeles
https://www.discogs.com/release/13343133-Raoul-Romero-Orchestra-Meditations-On-The-Zodiac-
and it seems Don Schlitten was the only one who regularly got Las Vegas musicians on his LA albums (Montrose with Frank Butler, but especially the series by Sam Noto)... so that does explain why Montrose was less involved in those 70s and 80s productions than others, in line with Larry's theory.... also, those David Holt productions were a bit obscure I guess (found one of them recently, it's ok but e.g. the Discovery albums of Jay Migliori or Bob Cooper, I like a lot better)