I guess for ex SPGers, the point were getting revalued (can redeem on those highest category ex SPG hotels with less point than SPG era) then got devalued a bit with the introduction of these peak and off peak rate
While ex Marriott, they got their point devalued as previously their Marriott category is quite closely match current categories.
I can guess after 14 September, those popular hotels is big cities will have more peak rate available.