That sounds a little too made up. An application being a 64bit application ordinarily means that it uses 64bit executables and libraries.

Additionally Valve have been on this journey to drop 32bit for a while. Last November they published a 64bit beta for Windows, in December they switched the Windows version to 64bit, in January they dropped support for 32bit Windows.

At the moment I have no reason to believe they didn't compile the Linux version for 64bit architectures as well now. That's why I asked if furry toaster had any evidence. Maybe there is something to change my mind.