Hmmm....good question. I used it to check my commute for this week, and it showed a tax.

Status was "Personal," not vacation or family vacation.

I had looked under one of the FAQ pages, and it said

"ALL pass riders must pay applicable taxes and fees."

Now, I had interpreted that to mean imputed tax for all, but the note you mentioned seems to make the above mean AIRPORT taxes and fees.

Still learning....

Taxes are only applicable to international pass travel. The only domestic passes I see fees on are First Class bookings. There's no fee for SA1 pass riders.