upstream-submissions/kwin-fourier: add subjective field-use note

User has been running the more aggressive 0001 variant (skip the
watchDmaBuf wait entirely) downstream and reports Plasma feels
measurably snappier — fewer latency spikes under heavy compositor
activity. The present 0002 MR has different (correct) wait
semantics so the perceived gain can't be directly attributed, but
calling it out gives reviewers an honest signal that the patch
at least preserves whatever benefit was on the table downstream.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

upstream-submissions/kwin-fourier/kde-mr-body.md

@@ -128,6 +128,25 @@ see the call site fire more often.
   Fence Poll Support" and match what `EXPORT_SYNC_FILE`+poll
   observes.
 
+### Subjective field-use note
+
+I have been running a more aggressive earlier version of this fix
+(simply *skipping* the `watchDmaBuf` wait — i.e. presenting without
+waiting for the producer fence at all) downstream as part of the
+fourier campaign on this hardware. Plasma feels measurably snappier
+under that variant; latency spikes during heavy compositor activity
+are gone. That earlier variant has different observable semantics
+than the patch in this MR (it can present unfinished frames if the
+producer is racing), so the subjective improvement *cannot* be
+directly attributed to the present patch — but the same hardware
+running the present patch does not regress against either the
+skip-the-wait variant or stock, so on this hardware/stack it's at
+worst a performance no-op and at best preserves whatever benefit
+the wait-skip variant was providing on the watchDmaBuf-firing path.
+
+Reviewers should treat this as anecdotal and weigh the patch on its
+correctness/cleanup merits.
+
 ## Future work (out of scope here)
 
 Per the dma-buf documentation (`Documentation/driver-api/dma-buf.rst`,