Not sure how "pessimistic" the checker is these days.
Depends on how they're doing the estimates I suppose. There was a significant revision a while back with most estimates increased but for my line they were still on the low side.
My estimate was 26.8 down 5.6 up, I'm 520m from the cabinet in a straight line - maybe another 100m for the wire route. If you look at the various VDSL2 rate/reach graphs they'd suggest > 40Mb/s at that distance (though maybe not by much) and, in practice, that proved to be the case as I get full sync.
They don't appear to have updated my neighbour's estimates, nor even mine as lines get connected and they get better data as to the real performance. Maybe they want to see whether the effect of crosstalk is as bad as some predictions as more lines in each cab get enabled.