That is correct, there was no preview update released near the end of April, this happens some months when the Microsoft engineers are working to fix problems on their servers, currently they are dealing with problems with Outlook, Teams and Copilot.
The last time this happened, the Preview update was not released at the end of the month, it was released in the first week of the next month, so, it is possible we may get that update next week before the May monthly update.