Keep in mind that this change for UA is ONLY for redeemable miles. So some important key points to keep in mind.
1) Their FF program (equivalent for Altitude) is unchanged. Miles are awarded on distance and NOT spend. With COS bonus for cabins.
2) Miles that can be redeemed are changing (equivalent only to Aeroplan).
Drawing a comparison to the Altitude program and this change is nonsensical for the reasons listed above. Comparisons can only be drawn to the Aeroplan program.
Also, as pointed out above. AC already does this and has for a long long time with the Tango / Flex / Latitude milage accrual differences.