Frame timing incorrectly shown if 3dlut is used with vo=gpu-next

Important Information

mpv 0.34.0-235-g84821dbcb6 Copyright © 2000-2022 mpv/MPlayer/mplayer2 projects
built on Mon Mar 28 12:22:33 UTC 2022
FFmpeg library versions:
libavutil 57.24.101
libavcodec 59.25.100
libavformat 59.20.101
libswscale 6.6.100
libavfilter 8.29.100
libswresample 4.6.100
FFmpeg version: git-2022-03-28-5ee198f9

If you're not using git master or the latest release, update.
Releases are listed here: https://github.com/mpv-player/mpv/releases

Reproduction steps

correct frame timings are shown in stats with these examples:
mpv --no-config --vo=gpu-next
mpv --no-config --vo=gpu --lut="C:\mpv\3dlut.cube"

but incorrect frame times are shown in stats with:
mpv --no-config --vo=gpu-next --lut="C:\mpv\3dlut.cube"

Expected behavior

frame timing should only slightly increase with a lut option

Actual behavior

frame timings are very high and close to 100%
However actual cpu + gpu load is fine and no dropped frames are visible.
This seems to be a visual bug in the stats only.
The same is true if target-lut= is used instead.

Start by reproducing the issue with mpv's vo=gpu-next, the --lut option, and target-lut=, then compare the displayed stats with vo=gpu and without a LUT. The fix is complete when frame timings in the stats remain close to the actual CPU and GPU load and do not approach 100% without dropped frames.