I think April was referring to this thread -
Hello, You are currently shipping a majority of your customer orders within one day from when the order is placed. However, the current handling time selection shows that it will take you longer to ship customer orders, which can affect your sales. Starting April 4, 2023, customers will be informed about the estimated handling time and your selling account will be updated to one-day default handling time, automatically. Note: No action is required from you and this change will only affect yo…
It sounds like Amazon has decided to automate individual SKU handling times too, along with your general handling time settings. But in either case, you should be able to avoid any Amazon interference by keeping the ‘automate handling times’ switch set to OFF.