Does UNESCO recognition apply to every Istanbul hamam?
No. Recognition of Istanbul's historic areas is not a blanket endorsement of every bath, operator or treatment. Check the actual listed area and building context.

Related questions
Does an old-looking hamam have to be historic?
No. Marble, domes and Ottoman-style decoration can also be modern. Look for documented construction and restoration dates if the age of the building matters to you.
How can I check whether a hamam's history is accurate?
Look for the building's own documented history, museum records and restoration research. Separate construction dates from later alterations and the current operator's marketing.
Does a Zeyrek bath booking include its museum?
Do not assume it does. Check the operator's current ticket and treatment terms; museum access and bathing can be separate arrangements.