I agree it sounds a bit exagerated.

Yes your air might be a bit denser ;-)
Something that definitly can be felt, when sailing at the lake of silvaplana (2000m above sealevel).

It was at the lake of garda (only 200m above sealevel), sailed with some friends (they sailed on a Taipan together) while I had to sail alone (my crew didn't show up) and they promised me to take care of me, in the case of capsize.

My downhaul was maxed out and so was my traveller...
I wasn't very fast and had trouble to get through the tacks.

When you often sail the 18HT alone, you defintifly wand a smaller main.