That's sort of true. Marriott publish their franchise documents online ("
US Franchise Disclosure Documents") which are very interesting, there's
over 600 pages about running a Courtyard franchise which includes the franchisee's obligations starting from page 80.
Additionally, Marriott has an Audit Program which is used to regularly review hotels and ensure they're compliant with the brand standards. Of course, Marriott isn't going to cut off a hotel just for a few violations, they're in it for the fees paid by hotels, but they do have remediation steps and hotels are held (a little) accountable:
Granted, from a guest's perspective, a process that takes
years to hold a hotel accountable to Marriott's standards is utterly pointless, so this is of little reassurance to guests, but for the sake of accuracy, there is standards and they are enforced.
What I wrote isn't sort of true, it's simply, true.
Yes, the parent company has rules which state that within a timeline a GM (and the sales manager) must become what they refer to as certified via doing company approved coursework either online and/or going to conferences, etc. But, the point is that the parent company does not filter or have a direct hand in the hiring process of anyone at the franchise location. Yes, if the GM does not become certified within that time frame, during the property's next QA audit that will be quickly found out and it is a major violation but, at the of the day the franchise owner hires the GM they want because they own the hotel, not the parent company.
Just like the owner and/or their management company decides pay rates, FTEs, hand book rules, what services the hotel will offer (i.e. we'll have a shuttle or we won't - we'll have a pool or we won't - what hours will those things operate if we have them - as long as all appropriate ADA requirements are met, what the breakdown of room types will be) completely independent from the parent company because again, it's their hotel. The parent company gives guidance or best practices as to what they think you should do, but you are free to do whatever.
As a sidebar on that, a very good friend of mine was recently hired to open a new FIS. He went to a lunch meeting with a VP from the franchise company that is the owner/operator and was hired on the spot after lunch. Was Marriott consulted? Nope. Does he start in three weeks? Yep. Has he ever worked at a Marriott branded location prior? Nope, all Hilton. Their hotel, they hire who they want.
As for your point about QA standards, that's funny. Nearly everything with QA is highly, highly subjective. While it's all in black and white, every auditor has a different spin on things. It's amazing how some will see the stained lobby tile grout and others "will miss it." Some will take points off for item X and others will just "note it" for next time. Just like every franchisee is out there trying to push the envelope as far as they can simply because it's to there financial best interest to do so. Can a property can fined or "held accountable" for pushing things too far? Of course but it's rare and it takes an awful lot over a very, very long period of time to get there.