I haven't seen a problem with loosening on any of the engines using the new style of mounting.
Briggs has been busy updating IPLs so things like part numbers are being changed without notes. On the IPL for your engine they don't list the older style PN anywhere in the downloadable IPLs from the Briggs Power Portal which is the dealers website. I can only assume that the part was changed back in 2011 as that is the time noted on the studs.
As for the above manifold here is a list of previous PNs that are listed in the last price file download to my system from Power Distributors.
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