Shaykh Albani weakened hadeeth of Prophet saw hearing from his grave Silsilah Da’eefah vol 1 n 203.

Secondly, the difference of Hayati and Mamati is not on the Prophet saw being alive in his grave or not, because both affirm Prophet saw is dead and death touches every body as established from Quran that Prophet saw will die. Sarfraz Khan said that Prophet saw being touched by death is dharoori belief in Taskeen Sudoor.

But then after death then they differ on the next life in grave wether it is duniyawi like life before death or barzakhi life that is different from the life of Duniyah.

For Hayati, it is same life like Duniyah, the Soul is in the Prophet's body. Prophet saw hears people next his grave, in fact his death is just like him being hidden, nothing changed from life of this world.

For Mamati, the Prophet soul is in higher company with Allah and separated from soul. And it does not return except on Judjement day.

For Salafee, then there is a link between Soul and body, generally the Soul of Prophet saw is in Higher company of Allah, and Allah turns it back to the body to answer Salam brought by angels, and it might turn in other times, but the link between them is not like the life of Duniyah, Allah told in Quran that death is not like life.