I don't think it's strange behaviour.
The supers forced them to do it.
I disagree with the interpretation of the "Supers forced them to do it", but rather it has been the plan all along.
AMD most likely has pretty much anticipated Nvidia's move all along, as there's a long track record of AMD releasing cards or establishing footing at within the price gap between Nvidia's offering and only to have Nvidia to release a card like 1070Ti to in attempt the ruin their parade. AMD may not be genius, but they certainly ain't complete moron that would fall for the same old trick over and over again. This is why I believe the initially rumour pricing of the Navi deliberately spread to be higher to throw Nvidia off, so that after Nvidia done with announcing their T̶i̶ Super cards, they can put the Navi at the true price segment that they have already planned to be at all along, rather than playing Nvidia's game on their turf. And as a result, Nvidia now looks REALLY bad with the 2060 6B vs the 5700 and the 2060 T̶i̶ Super against the 5700XT.
AMD knew their Navi cards didn't have the performance to compete against Nvidia's cards that are based on the TU104 cards (2070S and 2080), so the are exploiting Nvidia's nature/fondness of being stingy and milking the consumer with their lower tier TI106 based cards (2060, 2060S, 2070), and target that mid-range market segment instead. It's almost like AMD has taken a page out of Sun Tsu's Art of War:
"If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle."
AMD does not have an army as large as Nvidia, and their strongest warriors (graphic cards) ain't as powerful as Nvidia's stronger and strongest, so they have to pick their fights and choose their battles wisely.
