Syncing Upright Mode (Auto) doesn't recalculate per photo, each image needs a manual Update

Description of Issue:

When Auto Upright is applied to a batch of photos, Lightroom Classic does not run the Upright analysis on each photo. The other photos get a transform that looks like it was computed for the active/source photo. Each photo only gets its correct, individually analyzed correction after I open it and click "Update" in the Transform panel. On an interior shoot (kitchen cabinets) with dozens of frames, this means clicking Update on every single photo, which defeats the purpose of syncing.

This is NOT the known "uncheck Upright Transforms" issue from the thread "Batch Auto-straightening isn't working" (961997). I followed that accepted answer exactly and synced Upright Mode ONLY, with Upright Transforms unchecked. Same result: every other photo still needs a manual Update.

Lightroom Classic Version: 15.6 [202609251514-f839cde9], Camera Raw 18.7 (also reproduced on 15.5.1)

OS Version: macOS 26.5.2 (25F84), Apple M3 Max, 48 GB RAM

Camera Model: Sony A7R V (ARW raw files)

Steps to Reproduce:

1. Import several photos of the same interior scene shot from slightly different angles (strong verticals, e.g. kitchen cabinets).

2. In Develop, select all the photos. On the active photo, open Transform and click Upright > Auto. Verticals are corrected well.

3. Click Sync, check Upright Mode ONLY (Upright Transforms unchecked, everything else unchecked). Click Synchronize.

4. Go to each of the other photos.

Expected Result:

Each photo is analyzed on its own and gets its own Auto Upright correction, the same result as clicking Auto on that photo by itself. Syncing Upright Mode alone should trigger a fresh per-image analysis.

Actual Result:

The other photos show Upright set to Auto and there is a shift in transform, but the correction is wrong for them (verticals still off). The Transform panel shows the "Update" button, and only after clicking Update on each photo individually does Lightroom recompute and straighten the verticals correctly. Same result with Upright Mode + Upright Transforms both checked, with Copy/Paste settings, and with Auto Sync.

Workaround: open every photo and click Update one at a time. Syncing Upright Mode should trigger the recompute, or there should be a way to run Update across a selection.