It sounds like time of arrival. I do recommend checking the restaurant's hours, calling to verify the latest one can arrive and be seated (when does the kitchen close).
IMHO, requiring we leave before a specific time does not give a shopper time to finish a restaurant shop properly should any delays happen. Bundle in waiting to be seated, slow service, and potential food issues needing to be resolved, 90 minutes is not sufficient time for a fine dining shop.
A perfect situation for fine dining, without a separate bar visit, is 60 minutes minimum.
My posts are solely based on my opinions and for my entertainment, contact a professional if you need real advice.
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