Not sure. I work with four banks. Three want seasoning of six months and one wanted a year. I could have taken my purchase / rehab proposal to the bank for a 30 year with a construction loan on the front side and conversion on the back. You are right. By the time I got the rehab done, rental in place, and started shopping again, the six months came around quickly.
I don't know about commercial loans, but some hard money lenders offer products that allow a flipper to refinance or do a cash out without all the red tape and seasoning. These might be terms of only a couple years but interest only payments. Rates will be more than conventional but less than a short term rehab loan. This allows you to pull some money out immediately so you don't miss opportunities then you can refinance later down the road with a conventional lender.