According to MSDN BOL (Books Online) description on SOME | ANY (Transact-SQL),
SOME and ANY are equivalent.
<some> ::= SOME | ANY
I suspect the reason is that SQL language comes from the early 1970s, but had no standard until 1986. The standard would have taken elements of the existing SQL dialects, so we have this SOME/ANY anomaly.
This blog article by Brad Schulz explains some differences: "ALL, ANY, and SOME: The Three Stooges"