See now I've just looked at that again and something has caught my attention....
With G.INP enabled on Broadcom based kit the actual sync is normally more than the attainable...
For example:
SYNC:69319 ATTAIN:68284 (Taken from HG612)
Now I also saw this on the HH5A
For example:
6. Data rate: 19033 / 69194
7. Maximum data rate: 19033 / 69176
However oth of your samples as below:
HH5B:
6. Data Rate: 19999 / 76148
7. Maximum Data Rate: 24287 / 76746
HH5A:
6. Data rate: 19999 / 70778
7. Maximum data rate: 23506 / 72032
To me they both look like traditional fast path results.... I would say the '5A' looks Interleaved due to the 2000kbps unused in the attainable but this could be a bug or compatability issue with DSLAM.
PS. I'm not quiet sure how much you can trust the IP Profile system to be accurate either, I've found it to stick in the past, it has stuck taking 6Mb away from downstream throughput before now.