Yes, I do strictly think that Blizzard decides. Why you seem to show disbelief at what I wrote is puzzling. You could make a statement about the rules of supply and demand in an environment that has known variables and use it to back your claim up; you however have no numbers to work with in the case of the WoW token, which is why you can't talk about supply and demand as definite proof for your position. There is no way to determine whether the WoW tokens they give you for your gold have previously even been bought by someone in the first place, making the token system a mechanism that simply alternates between dumping and spawning gold.
No, the reason it didn't shoot up beyond the current margins is because they are not allowing it to; the amount of gold given for a token increased five to six times after WoD, while the amount of gold players can make through various sources steadily declined and required more and more tedious routines for much less. In fact, the example you've given with the MC Brutosaur backs up the claim that Blizzard artificially maintains the token-to-gold exchange rates because, if the opposite was true, the volatility would be much higher. There is only one logical conclusion to this: they're either spawning tokens on demand, they're setting an artificial token-to-gold exchange rate with marginal changes or both(which would make the most sense).
Logicically, the WoW token should be worth a lot less gold now than it was back in WoD and Legion because the amount of gold players can routinely make has drastically declined. In other words, the less gold players are able to pump into the virtual economy of WoW and the less gold there is overall, the more a single unit of gold is worth, which would lead to a steady decline in the amount of gold that is given for a WoW token. This however isn't happening and the reason why is Blizzard's artificial maintenance of what they percieve to be a reasonable exchange rate. There are of course other things to be taken into account, such as player activity, the addition of goldsinks and overall player numbers/engagement at a given time, but the more variables we add the more logical - if it was truly a spontaneous system - it would be for the token exchange rates to get increasingly and incredibly volatile.
A key takeaway here is that I am in no way trying to give this business practice of theirs a negative connocation; it's a profitable business practice for them and they have to maintain their system. It undoubtedly benefits both Blizzard and a great number of players. What is wrong however is to claim that this is a self-regulated and spontaneous mechanism. Standing firmly by what you are saying and believing WoW token gold exchange rates are regulated by "supply and demand" is in the domain of blind belief that goes against knowledgable judgement.