I don't think two handed bowling is a gimmick.
I think it is what those who aren't strong enough to go thumbless with one hand have to do. There is a guy here locally for many years that throws the ball a lot like Belmo with no thumb, and just one hand. You have to be very strong to do it, and he is. He is a great bowler. Has the average and scores to back it. Never seen him on truly drier conditions or sports shots, but have seen him in several different houses put up the numbers.
Those who are not that strong have to use two hands in order to support the ball and generate speed to bowl without a thumb.
As mentioned, speed and revs don't equal PBA titles. It takes a lot of skill and accuracy to go with it.(which all PBA bowlers have) My two favorites to watch bowl on any condition are WRW Jr and Norm Duke. The have the whole lane to work with, and many different angles.
"1 of 1."