Movie Render Queue does not render letterboxes to exports with sensor aspect ratios between 16:9 and 1:1

There is a discrepancy between how Movie Scene Capture (Legacy) and Movie Render Queue handle letterboxing for sensor aspect ratio's that do not match the export resolution, which seems to be a bug with Movie Render Queue specifically for sensor aspect ratio's between 16:9 (1.78) and 1:1 (1), demonstrated in the attached GIF:
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The frames have letterboxes burned in on render from either render method for most of the range:
 
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The exception is those frames with a sensor aspect ratio between 16:9 and 1:1 do not have their letterbox burned in on the MRQ render only:
 
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Using [Link Removed] (4.27):

1. Open Main map (default)
2. Open LetterboxTest_Animated Level Sequence in Sequencer

Or from scratch in 4.26 or 4.27 launcher versions:

1. Create level sequence and add CineCamera Actor
2. Animate camera actor's filmback sensor width attribute from ultra wide (i.e. 51mm) to ultra narrow (i.e. 4mm) over 3-5 seconds in Sequencer

Then:

1. Render to image sequence using Movie Render Queue option 
2. Render to image sequence using Movie Scene Capture (Legacy) option 
3. Compare frames 81-95 in each export (those frames with a sensor aspect ratio between 1.78 and 1) – Movie Scene Capture render has letterbox while Movie Render Queue render does not