Yes, marketing is often funny. I don't know where you find the cable spec of 24/48 though it might be right. Maybe I'll look for a better match. I could always try the $15 cable direct from google with no marketing claims at all: https://store.google.com/product/optical_cable_chromecast_audio. What I do know is that the Yggy is happily playing without the "get better gear" light coming on and so far it's lit up at 44x1 and 48x1 when I've looked. Oh, and it's fun and sounds great. In my opinion.
So, the first thing to say is that, if you're happy with it, then that's all that you should be concerned about. I only commented at all because if that cable only meets (and doesn't exceed) its spec, then it's not capable of delivering data at rates that Yggdrasil is cable of handling.
To answer your question:
The cable you linked to specifies a bandwidth of 6 MHz right in the marketing copy. Since marketeers are not well known for under-selling their products, lets be generous and assume they've actually tested the cable to 6 MHz and it passed in worst-case scenarios (if it had undergone and passed tests at, say, 11 MHz, which is what you'd need for 24/88.2, I would assume they'd make that higher claim instead).
The S/PDIF protocol, which is common to all TOSLINK implementations, uses a bi-phase clock - which means, in essence, two "ticks" are required for each transmitted "bit" of data. For each sample of data, there's a 32-bit (32 time slot) block of data per channel. This can carry 16-24 bits of audio-sample data (the raw spec is for up to 20-bits, some extensions permit it to use up to 24-bits), per block. Either way, stereo audio requires 64-bits of data, or 128 clock-pulses, per sample.
Multiply the 128 pulses per sample by your sampling frequency and that gets you to the required bandwidth (in MHz) of your cable. Which, in this case, yields: 128 x 48,000 = 6,144,000 Hz. Or, rounding a little, about 6 MHz.
Things like bend radius, length, the quality of the fiber (in terms of internal reflections) and, especially, the quality of the polish on the cable ends, might affect how a SPECIFIC cable operates, and as a result some cables, in some situations, might perform better, but in general the marketeers aren't going to claim it does less than it really does.
In short ... the people selling the cable aren't even attempting to claim it works beyond 24/48, so if it does it's a bonus. It may not be relevant to some people, but it's certainly not even claiming to be capable of delivering what
Chromecast is capable of, let alone reaching Yggdrasil's limits.
. I do understand that they work well for most.
