Yes that is a bit weird.
One foolproof way to test if the speakers are in phase is to play some bass heavy music, position the speakers facing each other and close together.
If in phase there will be plenty of bass, out of phase there will be hardly any.
No test kit required.
I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan