I made a quilt in the 1990's - and used a Kaufman fabric for the backing - I just assumed it was 45 inches wide - nope - it was only 42 inches wide.
So - even years ago, fabrics were not always 45 inches wide.
I have found that some even "better brand" fabrics will shrink a lot. The Roc-Lon tea dyed "pre-shrunk" muslin shrank significantly when I washed it.
I have not found any particular rhyme or reason to know when a fabric will shrink or not. I have measured hundreds of fabrics before and after washing them (really! I have because I was wondering if it was worth the effort),
Almost all of the woven cottons shrank some - most of them shrank in only one direction. Some shrank a lot - I consider over two inches of shrinkage on a 42 inch width fabric to be significant.