Actually, it's not just old winters. I counted 27 winters where there is a discrepancy, including multiple recent ones (1996-97, 1998-99, 2000-01, 2004-05, 2005-06, 2006-07, 2010-11, 2019-20, 2020-21, and 2021-22). The vast majority of the time NWS Pittsburgh's count is a bit higher but there are exceptions. Most of the differences are small - less than an inch or two. But some of the early winters, there are discrepancies of up to 10 inches.