"Automatically resize to fit contents" setting breaks pasting from Excel using "Merge Table"

I am seeing the issue described here: https://learn.microsoft.com/en-us/answers/questions/5432795/issue-merging-table-data-from-excel-to-word.

My workflow is:

1. Copy some cells from Excel
2. Click into an existing table in Word (of the same "width", ie: number of columns as copied) and paste
3. Select "Merge Table" (Windows) or "Merge With Exsiting Table" (macOS)
4. Rows are added to the table, with the content of the Excel cells mapped to them as desired

This worked up to 16.94. After 16.95, this process splits the existing table in two and adds a third table in between, making the first row pasted into a new header row. This weird new table will not merge with the other tables in the way an ordinary table can be merged with "Alt + Shift + Up".

I've tracked down that this issue does not occur if "Automatically resize to fit contents" is ON. If it's off (as in our templates), the table splits into three when "merging"!

(I've tried several times to post this to Microsoft Q&A, but I keep running into errors. To be honest I'm now thoroughly confused about which forum a general customer is allowed to be on and use…)