That works for me. I have FFmpeg installed and the file imported even with the WAV header and file extension.
Back in the early days of the Internet, Internet Explorer had very poor support for media files. A workaround for that was to “wavify” MP3 files - that is, to encapsulate MP3 files in WAV headers so that IE would play them. It was not a particularly “good practice” thing to do, but it worked at the time and it saved bandwidth for people on (slow) dial-up modems. My guess is that these files date back to that bygone era.