Looks like Business Awards (and most classes of paid business tickets) will have to pay to pre-select seats for tickets purchased on or after June 1.

Finnair's Punitive New Seat Assignment Policy - One Mile at a Time

Finnair addresses the excess carry-on baggage issue with the new Superlight ticket type and changes to baggage allowances | Finnair Finland

There's a buried sentence in the second article stating FinnairPlus members still retain advance seat selection. TBD how that would work if you're a FinnairPlus member but purchasing an Award ticket through AA or another OneWorld partner.