AMD HW H.264 (AVC) HQCBR and HQVBR ignores bitrate settings

Operating System Info

Windows 11

Other OS

No response

OBS Studio Version

30.1.2

OBS Studio Version (Other)

No response

OBS Studio Log URL

https://obsproject.com/logs/pEvB87fs4SfOBF33

OBS Studio Crash Log URL

No response

Expected Behavior

The resulting bitrate corresponds to the indicated in the settings.

Current Behavior

The resulting bitrate does not even closely correspond to the indicated in the settings. For example, I set 6 Mbps. In simple scenes bitrate will be ~20 Mbps, in complex ~140 Mbps. This is displayed both in the Stats window and in the properties of the resulting file.

Steps to Reproduce

1. Output Mode - Advanced
2. On Recording tab:
   Video Encoder - AMD HW H.264 (AVC)
   Rate Control - HQCBR or HQVBR
   Bitrate - 6000 Kbps
   It seems the rest of the settings does not affect this.
3. Start Recording

Anything else we should know?

AMD Adrenalin version 24.5.1
The problem is present only with AVC. HEVC and AV1 work as expected.
This behavior is very similar to CQP ~20. Clarification: CQP value displayed in the log is not related to this problem.

Start by reproducing the issue with OBS Studio 30.1.2 on Windows 11 using AMD HW H.264 (AVC), HQCBR or HQVBR, and a 6000 Kbps bitrate. Compare the OBS log and resulting recording bitrate with the expected setting, and verify that AVC is corrected without regressing the working HEVC and AV1 paths.