in 2007ish when USBC changed the requirements for the softness of bowling balls, particle material wasnt really able to used as much because it was to soft.
I believe what he is referring to is when they changed the MOH's Hardness specification back in 2005 in regard to materials used in coverstocks. (such as the particle materials)
Which is not the same and is a separate specification than the durometer "D" hardness scale (which stayed the same at 72) which is used to measure the ball's overall hardness or softness.
These specifications are listed in the Equipment & specification manual under the "Physical Specifications" section.
Hardness Min:72 Max:None
Mohs’ Hardness Min:None Max:6.0
"2.
New Mohs' Hardness specification.
Mohs' hardness is a material hardness scale that differs from the current durometer "D" hardness scale.
It was developed by Fredrich Mohs' in 1812. Hardness of a material is determined by observing whether its surface is scratched by a substance of known or defined hardness.
The Mohs' hardness of any material added to or included in the coverstock of a bowling ball shall not exceed 6.0 on the Mohs' hardness scales tested in accordance with the USBC approved test procedure. A standard glass sample with a Mohs' hardness of 6.0 will be used to determine if the materials in the cover stock of a bowling ball will scratch the standard glass sample.
Any ball with cover stock material that is harder than 6.0 will scratch the sample and that ball will not be approved.
The standard glass sample will be manufacturered by an independent contractor specifically for use in this test. The test method is very simple and can be reproduced at the ball manufacturers lab.
This will be implemented by 8/1/05. The current durometer "D" specification will remain in effect."