If you get that pressure build up in your head then you are blocking the wrong vessel, to be exact: the jugular veins, which let blood flow from your head to your heart. Instead you wanna rather compress the carotid artery. But that takes a lot of training to block the carotid artery while (in the best case) not blocking jugular veins and your airway. But a lot of people have problems with that. Also it doesnt help that the jugular veins only needs like 2kg of force to block and the carotid artery needs like 5kg which means, if you dont position the rope/scarf/whatever not perfectly for your anatomy you are always above threshold of not blocking the wrong vessels (jugular veins).