u/Choco-Cupkat

I am playing Thomas Morely's 4 Fantasies (pics from Il Lamento). Are these square notes just supposed to be harmonics over these notes? The one youtube video I saw online is not playing these as harmonics (but it's not a professional performance) so I am not really sure what to make of them. Videos I saw with other instruments (not cellos) are also playing Gs at the end so not the pitches the harmonics would be, but then I am not sure what the square note should mean? Any help appreciated.