This holds true for the original characters and for the characters I inserted. Placing my cursor in the document in an paragraph correctly showed me that it is based on 'Normal' template (or whatever template element it was set in). When I typed in a blue heading 1 which was set in Georgia 14pt, I ended up with having blue TMR 14pt heading 1. So when I typed in an word set in Arial 12pt, I got TMR 12pt for my newly typed characters. On further investigation, I found out that size and font color was used correctly from the given document/template/formatting but the font itself was Times New Roman (TNR) all the time. When I am started a new dotx file, everything I was typing was in Times New Roman instead of the pre-defined font. When I opened any given docx file in my Word (Office Professional Plus 2016) and I started to type within an existing paragraph which is set in - let's say Arial font, I end up with my characters set in Times New Roman. Spoiler: it re-appeared and could not be fixed for good. I had a very stupid issue with Word 2016 on my office computer and this my story about the journey to solve it which took me a couple of months. : Yet another link to a potential solution in 'Further Approaches'.

: Section 'Problem Reappearing (Again)'.

Word set default font word 2016