Here is a simplified MAX file. Unique Download Link | WeTransfer
The main issue is cleaning the Indirect light. Even the direct light is taking longer to clean.
And this is not happening only in this file, all our files we have to increase GI to AA level and sometimes the Light Samples Multiplier.
Interesting, so is it confirmed that the new sampling is slower more often than not or how should we go about this? maybe default GI vs AA should be 32 instead of 16?