Thanks for the exhaustive documentation of the issue. That’s very appreciated.
The issue is not in your implementation but in SNAP and should be fixed with the next major release.
https://senbox.atlassian.net/browse/SNAP-1461
The issue description is about multi-size but when looking at the solution also single size are affected.
You could add another subset operation to overcome the problem in the short-term.
There you could define the pixel region. Retrieve the width and height from the previous subset result and subtract one.
This should give you the desired result.