BE for short-length multi-byte integers is an aberration; all architectures become LE at some bigint granularity.
To understand why this is the case, imagine a multi-precision increment of [0xff; 256] performed BE, where outputting the result for each byte from high to low has to be suspended until the least-significant 0xff byte is incremented and its carry-out status known, with the awaited carry then propagating back across all the higher-order 0xff bytes, low to high.
As @hsivonen has pointed out, BE is going away. Thus the endianness for any portable hasher needs to be LE.