I wouldn't read too much into it,some of these world records aren't anywhere near having all the time squeezed out of them.Where as others are super competitive and like you say only have 10th's here and there to gain.Some will have been set some time ago and never revisited,i know I'm a faster driver than i was 6 months ago,I'm sure it's the same for the top guys!
Just last week I did a TT on Sinclairs in the Renault RS01,on my 2nd lap I got the WR,over a second ahead of Kie25!!Now I know I'm not that good,so in reality Kie's lap was probably a quick try out to see the RS01.(Arsenalkid took more than a second out of me since then,and he hates Sinclair
Looking at Youtube,TRL looks genuinely quick,with quite a few WR's,wouldn't it be nice to have a livestream with a handful of the elite drivers taking on couple of TT events?