Coming from a very small village (population around 3000), that was absolutely the case back then. The very few people that were dealing, sold everything they could sell.
Anecdotal evidence: I met someone on the road (massive city, never saw the guy again) who tried to sell me some weed. I didn't want it and he ended up gifting me a small amount.
That said, I think the gateway drug phenomenon is a ridiculous theory.
There are people who are going to try any drug they can and there are people who are going to research the subject and just do drugs they deem to be safe / not addictive.
I don't think that the gateway drug theory holds any water. With that said, I do think a lot of users end up trying harder stuff because they're with the wrong crowd.
For what it's worth - I don't use anything. But I have friends who are regular users. Some use a lot of different stuff.
I've been told that whenever cannabis (here in Europe, that's usually hashish) dries up, there's always going to be people that turn to harder stuff. Apparently after COVID hit, hashish became very difficult to get, and people started dabbling with speed, etc.
This sounds like one of those 90's scary stories. Do you also believe that the first dose is free?