Romy, this may be due more to the Win32 limit of 2 GB as the maximum size of a file mapping object, at least in Windows NT and Windows 95 (the first 32-bit versions of Windows, to which WaveLab was originally ported from Windows 3.x), than it is due to any inherent limitations in NTFS today.
Internally, a chunk in a RIFF file (a WAV being a kind of RIFF) has a size indicator which is an unsigned 32-bit integer. A chunk's size should technically be able to reach almost 4 GB, but many programmers working in C/C++ (the typical application languages at the time WaveLab was written) use "int" as their default data type all the time, and don't necessarily distinguish carefully between that and the "unsigned" or "unsigned long" data type. If so, a chunk size greater than 2 GB would appear to wrap around to a large negative value, and I wouldn't expect most older software to know how to deal with that. Back when this generation of code was written, hardly anyone had that much space on their entire hard drive.
--best regards