Poor PPPoE Uplink on 4600 in TDD mode

Has anyone noticed very poor uplink speeds when using PPPoE Connections on AP with TDD Mode enabled? I have tested a 4600 connection where it has a link test of 623/338 with a 75/25 split.

PPPoE Test 430/160
DHCP/NAT Test 440/320

Using WLR mode and PPPoE I get 770/340 so it seems the PPPoE server is capable of pushing more than the 160 I can get with TDD.

Is this a known issue with TDD, and should I expect it to be improved anytime soon?