I think you are right on the money...16-bit vs 32-bit API calls.
For comparison, here is the HPFS386 specific example (direct copy from the Toolkit INF files):
=== START ===
#include <hpfs386.h>
#include <netcons.h>
 
HPFS386GetInfo16(pReserved, pszInfo, sLevel,
           buf, usBuflen, pusBytesAvail);    /* 16 bit */
 
HPFS386GetInfo(pReserved, pszInfo, ulLevel,
           buf, ulBuflen, pusBytesAvail);    /* 32 bit */
=== STOP ===
Here is another example, this one aligned with the naming convention you see:
NetDASDGetInfo or Net32DASDGetInfo 
=== START ===
#include <neterr.h>
#include <dasd.h>
 
NetDASDGetInfo(pszServername, pszDirPath, sLevel,
        buf, usBuflen, pusBytesReturned);    /* 16 bit */
 
Net32DASDGetInfo(pszServername, pszDirPath, ulLevel,
        buf, ulBuflen, pulBytesReturned);    /* 32 bit */
=== STOP ===