What happens if tile and a half is not used on the endge of a roof?

I think they are referring to the roofer having used cement fibre slates. Yes they should use tile and a half on the verge as apposed to half of a tile which is only 150mm wide. These small tiles might not be so well secured and tend to curl up a bit with the sun on them for being so small. Has the roofer put copper rivets on these small cuts to help prevent this happening ? Basically its not the done thing and he was cutting corners and saving a few pounds by not buying double slates.

Honestly it's no big deal. As long as mentioned previously the slate is fixed and riveted . In the ideal world slate and halfs will be used up the abutments and verges but there plenty of times wen most roofers will have used a half tile instead