The request is about to encoder quality level.As the encoder in VAAPI driver is improved and more encoder quality level is added for AVC/VP8/HEVC. Now upstreaming is on-going. here VP9 is ready in driver. The middleware should support this.
Legacy Encoder at most support two quality level. And new encoder support level at most 1-7.
Thanks for your bug report, but GStreamer tracks bugs in GNOME bugzilla at
Please file any bugs or patches there. We use the Freedesktop bugzilla only for account reuqests.