The 63 character limit on domain name labels in RFC 1034/1035 isn't arbitrary, it's a limitation in the way DNS packets are encoded. The upper two bits of the label length are used for compression of labels in DNS packets.
Without protocol changes, DNS cannot support labels longer than 63 bytes.
However, I agree that validating it is unnecessary.
Without protocol changes, DNS cannot support labels longer than 63 bytes.
However, I agree that validating it is unnecessary.