Yes, they are! The written rules can be found on page 35, section 38.3 of this document: assets.contentstack.io/v3/assets/blteb7d012fc7ebef7f/bltb6d44fb70a52ebd8/659c430b90dcf2a632648add/USA_Boxing_Rule_Book_Rev._01.01.2024.pdf
Thanks for the suggestion! The reason we label five yards is because hands come in many shapes and sizes. 5 yards is the regulation amount allowed. so that five yards can be adjusted to the hand size. Hope this helps!