Here I am giving unconfirmed sources. In Kurma Purana II.39.56-62, Shiva says
Indeed the holy Pasupata vow has been formerly designed by me for the achievement of liberation. It is the greatest of all secrets. It is the subtlest essence of the Vedas... Sruti states that this Pasupata Yoga should be resorted by the seekers of liberation
But later it is written
There are other scriptures opposed to the Vedic view. They have been propounded by me alone and they are very fascinating in this world. Those cults are Vama, Pasupata, the Soma cult, the Lakura (Lakula) and the Bhairava and such other cults which are opposed to Veda should not be resorted to.
Shiva is contradicting himself? This says Pasupata scriptures (containing details of Pasupata vow) are opposed to Vedic view... which is the exact reason why it should not be resorted to... not because of followers !! And later who says these things -
One should not even verbally revere and honour the heretics, those who indulge in wrong actions, those who perform black magic, the Pancaratras and the Pasupatas. (Kurma Purana II.16.15)
Hence, O bull-bannered lord, we shall compose scriptures for deluding the sinners and for saving those who are out of the pale of the Vedas.’ Thus addressed by Visnu, the slayer of Mura, Rudra composed deluding Scriptures and Kesava too did the same, on being urged by Siva. They were the treatises of the cults of Kapala, Nakula, Vama, Bhairava, both of Western and Eastern variety. Pancaratra, Pasupata and thousands of other cults as well. (Kurma Purana I.16.117-9)
Again - how can it be for both deluding AND saving people?
Those various scriptures which are contrary to Srutis and Smrtis seen in this world, are based on Tamo-guna or ignorance. Belief in them or practising in accordance with them is a Tamasa activity. They i.e. those contrary to Vedas are the cults of Kapala, Bhairava, (v.1. Pancaratras), Yamala, Vama, and Arhata and others similar to these also. In another incarnation of mine, these scriptures having been promulgated by me to delude the people who themselves try to mislead other persons by propagating their false scriptures. (Kurma Purana I.12.261)
That Sraddha wherein the wicked Tamasikas such as old Sravakas (Buddhists), Jainas, knowers of Pancaratra, followers of Kapalika and Pasupata sects, atheists, and others like them eat food offered to gods, does not bestow excellent benefit here and hereafter. (Kurma Purana II.21.32-33)
Who is saying these things or telling these stories? Is it interpolation? Because Shiva, Skanda and other Shaiva puranas are also highly praising these sects / cults