There have been proposals about shortening much further: in fact, the long-standing practice in the PKI community is that renewing certificates every 7 days is short enough that no revocation service is necessary at all. However, trying to move the entire IT industry to a 7-day renewal window is a bridge too far at this point!
Instead, I would surmise this is the first step in that process by introducing a window short enough to act as a forcing function on automating certificate issuance & renewal. It's short enough to strongly encourage leveraging automation everywhere possible, but not so short that one could argue it's impossible to do manually for things that still just can't do this automatically, of which there are still a disappointingly significant number.
Once we begin to get below 30 days, however, I suspect there will be a lot more scrutiny around the data suggesting exactly how small a window is sufficient. From a risk standpoint, if we're arguing shorter-is-better, then we should go as short as possible: someone will need to pull together the data that suggest exactly how small a window appropriately balances the various risks involved. (And then 15 others will need to argue about the validity of the data, whether the data actually suggest that, whether the data were assembled with an agenda in mind, etc., etc., etc.).
3 days is far too short. The certificate supplier could have a crucial piece of equipment or software stop working and 3 days might be too tight a timeline to get it fully resolved which then leads to lots of people having invalid certificates and the certificate supplier would be out of business shortly afterwards.
OSCP stapling except without the oscp stapling part.