I have received this reply from MSUK Technical
Dear Steve
The Asterisk next to a listed tyre is an indication that the tyre may be removed for the following year. It does not mean that the tyre is ineligible this year, and it won’t be removed during the year.
The tyre list are compiled by the individual manufacturers, who advise Motorsport UK which tyre products they support for inclusion on the lists.
NOVA Motorsport who represents the AVON products on the tyre lists, requested the listing to be annotated with the Asterisk in 2025 for the following reasons, which they confirmed by email to me today;
The asterisks on the ZZS and ZZR were added because, due to regulatory changes, we will be unable to produce these tyres in their current specifications moving forward. However, we do have significant levels of residual stock and are closely monitoring inventory levels both within the marketplace and through our UK dealer network. We currently do not anticipate removing these products from list 1B until at least 2027 for obvious reasons.
The Asterisk is there to give advance notice that the tyre may be removed, so that competitors can make informed purchasing decision, we will always give at least one year of notification, but the tyre will not be deleted from the list until the manufacturers requests deletion, once they consider the product to have been out of production for long enough that existing tyres have been used up.
I hope this clarifies.
Best Regards