This reminds me of the first time Jazz's leg raised. We were outside and he was weeing, when suddenly his leg slowly raised up. Jazz looked back at his leg like " what are you doing?"
He has never marked inside. He's pad-trained now- when we got Mo we had to pad train him because Mo would panic and have diarrhea if crated. So we thought it would be easier just to pad train both.
Jazz rarely raises his leg now, because he's had knee and hip surgery, maybe? He and Mo were both neutered at 8 months and both squat and neither mark.