That's not how tag managers work. Tag managers are managed by the website who pays them (it's yet another SaaS), and the website can put whatever it wants there

That's not how tag managers work. Tag managers are managed by the website who pays them (it's yet another SaaS), and the website can put whatever it wants there. Various site functionality could break if parts of the site logic is missing. You can argue it is bad engineering, but it isn't exactly the tag manager's fault any more than it is the CDN's fault.