Yes, but false advertising may still be a claim, even if there is no concrete agreement. And the legal standard there doesn't even require overt lies. That is, even statements that are technically true but misleading such that a reasonable person would conclude something untrue can meet the test.

And, in this case, documentation regarding the way their system works, as well other of their materials was overtly untrue. Beyond that, customers would merely need to show damages and also that Heroku profited from its untrue statements.

Whether it intended to mislead or not, Heroku could have a real problem on its hands.