+1 on this. I'm just working on my first few tables in Affinity Publisher (after roughly 15 years of tables with InDesign), and I basically end up setting all the column widths by hand again and again. Sometimes, InDesign gets weird in that respect too, but there I can just run an AppleScript to set my column widths the way I want them to be.
Exactly as you said in your previous post, when I paste into a table from Excel, there's a bug where an extra column gets tacked on. That also happens when copying and pasting from another text frame in Affinity Publisher. When I remove that column, all the other column widths change. At least when I resize the text frame that contains the table, all the column widths go back to where they were before inserting the text into the table.