A GOOD QUESTION, ANYWAY.
We are now asked a question from a local manufacturer of which particular ITTF Rule includes prohibition of the rubber topsheets with an extra coating.
For an answer please look into the Iater edition of ITTF M4 Racket Coverings document, re-named from ITTF T4.
Go to this page directly and then skip to the M4 document.
https://equipment.ittf.com/#/equipment/manuals
M4 document states as follows
2.4 APPEARANCE
The rubber surface of the racket coverings shall be
⚫ uniform
⚫ without coating
⚫ matt
SOME VEXED CRITICISM ON THE DOCUMENT USABILITY FROM MYSELF.
-- Regretfully, the cross navigation over the later edition M4 set my ass on fire. The document has got far worse layout, totally unreadable and inconvenient for readers to use.
The editor in chiefe should have a better knowledge of preparing .pdf files.