Definitely a lot of confusion. The FAA is encouraging pilots to obtain additional training when necessary (not wait for a flight review every 2 years). They stress that currency doesn't equal proficiency and flight instructors should promote this philosophy (which I agree with). The actual regulatory requirement has not changed.

Actually Merriam Webster lists biennial as one of the two definitions of biannual. This is just one of those oddities found in the english language that doesn't make much sense. But it is a correct use of the word nonetheless.

And why a flight school should never promise a sign off after a 1 hour flight. If you haven't flow in 10+ years, a one hour of ground and one hour of flight is unlikely to make you safe.

Having just competed my Flight Review after a 10-year hiatus, I concur. The instructor that I started with said he's found it usually takes 2hrs of flight for every year a person has been away from flying. I got my sign-off at just under 22hrs of flight instruction.