Are you sure this is not just learning inertia? Because frames in Affinity work more like css object-fit and are "live". In Indesign you have to "recalculate" fit/fill every time with action. I would argue if you didn't know Indesign way the Affinity way is superior.
Text rendering algorithms are quite known quantity and lifted from LaTeX. Indesign has paragraph (multi-line) composer which in latex equivalent is microtype package. Affinity doesn't have that but paragraph composer is not really used that much in professional setting because when you do final manual fixes/adjustment of typography then with paragraph composer your changes could affect previous changes in paragraph (so people go by line by line). Paradoxically paragraph composer is pretty good for quickly getting OK enough results especially in more budget/non-pro setting.
Other than that i don't think the typography output (for print) is different I've seen some tests and it seems kinda exactly the same. Affinity might render type on screen a bit differently but the output is solid. I was more afraid of the quality of .pdf itself but even highend offset printers didn't see a difference/complained.
Text rendering algorithms are quite known quantity and lifted from LaTeX. Indesign has paragraph (multi-line) composer which in latex equivalent is microtype package. Affinity doesn't have that but paragraph composer is not really used that much in professional setting because when you do final manual fixes/adjustment of typography then with paragraph composer your changes could affect previous changes in paragraph (so people go by line by line). Paradoxically paragraph composer is pretty good for quickly getting OK enough results especially in more budget/non-pro setting.
Other than that i don't think the typography output (for print) is different I've seen some tests and it seems kinda exactly the same. Affinity might render type on screen a bit differently but the output is solid. I was more afraid of the quality of .pdf itself but even highend offset printers didn't see a difference/complained.