In older basic rules, there were fewer classes but each had two subclasses. So depending on when someone last looked at the basic rules, it can be different.
The Basic Rules/SRD for D&D fifth edition (the only Basic Rules that matters to this conversation) has only ever had 12 classes with 1 subclass each
Not trying to be argumentative, but I'm looking at an offical physical copy (5e) with two subclasses for Wizard, Rouge, Fighter, and Cleric. I don't know what to tell you other than it's out there somewhere and people can get confused when it doesn't match online. I had one player in a group I ran that brought it up because they couldn't find the subclass they swore was in the basic rules. I validated that I was seeing the same thing, but figured it was just updates since the rules were older and they played something else. So when people say they can't find something in the basic rules they think should be there, I always think of this scenario.
Also, the basic rules downloaded from Wizards only has 4 classes (v1 released 2018 but only lists 1 subclass each). Here it has more, and while it lists two subclasses available, it only details one which leads to confusion (some quick ref links here and here so ya know what I'm talking about). So something changed which is fine, but this can confuse new players if they're not looking at updated sources.
The answer to your issue is likely here Official Wizards of the Coast Errata
I expect to see more issues like this when the new core rule books come out.
It is also why book ciphers work so well.
CENSORSHIP IS THE TOOL OF COWARDS and WANNA BE TYRANTS.
Ok that just made me laugh. So true!