I think you are right. I did a quick test with the original with qaac -V 91 both before and after reducing it by 3 dB in Audacity. I went from 20/20 to 9/20.
Original:
foo_abx 1.3.4 report
foobar2000 v1.2.4
2013/04/17 17:03:08
File A: E:\abx\original.flac
File B: E:\abx\qtaac-tvbr91.m4a
17:03:08 : Test started.
17:03:17 : 01/01 50.0%
17:03:28 : 02/02 25.0%
17:03:35 : 03/03 12.5%
17:03:42 : 04/04 6.3%
17:03:52 : 05/05 3.1%
17:03:57 : 06/06 1.6%
17:04:04 : 07/07 0.8%
17:04:09 : 08/08 0.4%
17:04:15 : 09/09 0.2%
17:04:23 : 10/10 0.1%
17:04:29 : 11/11 0.0%
17:04:35 : 12/12 0.0%
17:04:42 : 13/13 0.0%
17:04:48 : 14/14 0.0%
17:04:54 : 15/15 0.0%
17:04:59 : 16/16 0.0%
17:05:03 : 17/17 0.0%
17:05:10 : 18/18 0.0%
17:05:16 : 19/19 0.0%
17:05:22 : 20/20 0.0%
17:05:33 : Test finished.
----------
Total: 20/20 (0.0%)
Original -3dB:
foo_abx 1.3.4 report
foobar2000 v1.2.4
2013/04/17 17:05:48
File A: E:\abx\original-alt.flac
File B: E:\abx\qtaac-tvbr91-alt.m4a
17:05:48 : Test started.
17:06:01 : 01/01 50.0%
17:06:09 : 01/02 75.0%
17:06:19 : 01/03 87.5%
17:06:33 : 01/04 93.8%
17:06:45 : 02/05 81.3%
17:06:55 : 02/06 89.1%
17:07:04 : 02/07 93.8%
17:07:13 : 03/08 85.5%
17:07:19 : 04/09 74.6%
17:07:30 : 04/10 82.8%
17:07:38 : 04/11 88.7%
17:07:56 : 05/12 80.6%
17:08:09 : 05/13 86.7%
17:08:27 : 06/14 78.8%
17:08:41 : 06/15 84.9%
17:08:50 : 06/16 89.5%
17:08:58 : 07/17 83.4%
17:09:09 : 08/18 76.0%
17:09:21 : 08/19 82.0%
17:09:33 : 09/20 74.8%
17:09:42 : 10/21 66.8%
17:09:49 : Test finished.
----------
Total: 10/21 (66.8%)