I have the same theory. Anytime I see someone having a phone call on speakerphone it’s almost 100% because their screen is shattered and they just walk around screaming into their phone.
Makes sense that these are also the type of people walking around just raw dogging life with out a cell phone case.
If the phones that old it should have a 3.5mm jack. You should be able to plug it into an audio recorder and get the best quality.