Altering the deal is SOP where law permits it. Read any privacy policy or user "agreement" and note that they all have "Darth Vader" clauses where they get to alter the deal when ever it suits them. It's even your job to spam refresh on the page and use a diff tool to figure out what changed.
The difference is that these customers potentially can defend themselves with lawsuits and switching to a competitor.
In a sense, those clauses seem like the embodiment of a best alternative to a negotiated agreement. They reserve broad leeway to account for possibilities that might not have been anticipated; for the fact you can never anticipate everything. They are tolerated to the extent to which they are applied conservatively for this implicit, reasonable purpose.
The problems arise when some cowboy executive comes in and reads the letter of the law without regard for the spirit of the law and starts thinking they can get away with radical innovations that destroy the stability of the business ecosystem. Business partners in a contract may grant broad leeway conditioned on the trust that it will not be abused, but now that trust has been destroyed, how can you continue to do business with such a counterparty?
The difference is that these customers potentially can defend themselves with lawsuits and switching to a competitor.