Font Typeface Question

I am working on a document using either Calibri Light or Helvetica Neue Light font/typeface. I have no problem bolding words, but, in both fonts, if I remove the bolded emphasis the word does not revert to the light typeface but the regular typeface.
If it helps any diagnosis, I added the Calibri family to Font Book by dragging them from Word’s font folder in finder. When working in Word or Pages this issue does not replicate itself, but it does in TextEdit. My working assumption is that Word and Pages might simply handle fonts differently from Scriv & T.E., where the lack of an, admittedly counterintuitive, light bolded typeface forces the use of the regular bolded typeface) and thus creates the problem in the latter but not the former.
Any help, guidance, or clarification would be appreciated. TIA.