I really think this is a casualty of LB's production techniques clashing with band members' opinions rather than anything else. Lindsey extensively uses varispeed (literally, recording at variable speeds and then speeding the track back up to allow for rapid solos and some pitch alteration) in his solo recordings, and although that technique was kept for the SYW songs that were recorded for the aborted version of GOS, none of the other songs make any use of varispeed on any main track (rhythm guitar, drums, etc.).
When LB produces, he tends to record initial tracks at a slower tempo and then use varispeed to come up with a faster, glossier final track... we hear this technique all over Mirage, TITN, OOTC, etc., but it hasn't been used on a core track of any FM song since the TITN era. If you listen closely and compare LB solo with recent FM work, I believe the dichotomy becomes clear.
Personally, I don't believe Mick's age-related playing ability has any significant bearing on this, and even if it were the case it certainly wouldn't be a barrier in the studio given the varispeed technique discussed above. Songs like EOTW and Mick's WT solo were as fast and aggressive in 2013 as they were in 1997 (minus the hand drum, which was cut out for time constraints).
Just my .02
