
As said, the length of the tie doesn't matter. And even with slip ties, provided the bitch is right on, and the male viable, a pregnancy should occur. One of my stud dogs never managed a tie but he only missed to one of the bitches I let him be used on (probably no more than half a dozen). She came back to my other male, nect season, had a couple of good matings, and missed again. ..... taken to another male in another kennel, on her next season, she again missed. At which point her owner packed it in with her. With his slips, we'd upend the bitch for a little while to allow (we hoped!) the semen to get where it was needed.
Breeders prefer to see a tie, however long for, but it's not necessarily necessary

Oh and one of my bitches was vocal during the mating, and again on whelping. There was really no reason for this - it was just her and further, she'd have nothing to do with their poohing (peeing fine, but the other) which was left to me to sort out. She only had the one litter - 2 of which we kept!