Don't know about your friend, but Transgo used to recommend blocking it for hard street use or racing.
So a person that wasn't around them long enough to know or remember that has a hard time convincing me that his buddy might be right. Sorry
There is a lot of leeway in "street" because I know people that run 500 or more horses on the street and burn tires for 2 blocks. :-)
I would say for a general all around street cruiser, you could leave it in and it would'nt make much difference.
The statement was that it made no difference, and that is simply not true.
A lot of people also have no idea that it promotes increased clutch material wear from letting things slip as it releases the pressure on the clutches and band.
No spring releases faster as well as applying faster.