As Lillian says - there is no doubt that boar taint exists, and some people are very sensitive to it.
However we have not experienced it, and do not castrate. Indeed we have used boars a year old to impregnante gilts and then chopped them with no problems.
In England, castration comes under The Mutilations (Permitted Procedures) (England) Regulations 2007, and in Wales under the The Mutilations (Permitted Procedures) (Wales) Regulations 2007, both of which state under schedule 3 part 1
1. Castration
The method used must not involve the tearing of tissues.
An anaesthetic and additional prolonged analgesia must be administered where the animal is aged 7 days or over.
Section 5 of both regulations permits castration by a non-vet if carried out within 7 days.
Don't know scotland offhand, or if it's 4 days there.