The Dolby Digital track is actually compressed, not uncompressed as the author speculates. Back then, "Dolby Digital" branding was still synonymous with the Dolby AC-3 codec, which offers lossy audio compression.
Although interestingly, Dolby Digital on film isn't exactly AC3 - it's an earlier version that's incompatible.
The article miscalculates the data rate as "584KB/s (Kilobytes/s)" when the numbers actually give 554kb/s (using the patent's 5776 bits per square). This is kilobits per second, not kilobytes per second. The incorrect kilobytes number is more than enough for 6 channels of uncompressed CD quality audio, but the real number requires lossy compression.
Interestingly AC3 (with Joint Object Coding) is also what Apple Music uses to deliver Spatial Audio, although the OS makes it difficult to decode to any layout beyond 5.1.