Bobcat pioneered and patented the standard system 30 years ago, that have been used on all the loader brands built in the last 10 years or so, (since their patend ran out) as a result many older loaders use their own oddball QA. Some early loaders did not even have a QA.
If you don't plan to have many attachments, or want to buy, rent or borrow, then a non standard QA is fine.
However imo the skidsteer concept really started to fly when the patent ran out and any Joe attachment manufacturer that had a good idea could build one attachment and sell it to someone with any brand of loader, because now they were all the same.
We are in the process of converting one of our farm tractors right now from the terribly sloppy Allied QA with 2 loose pins to lock the bottom to skidsteer.
I'm not sure at what point Thomas switched to the standard, or yours may have been updated to. But I don't think it was from the factory. And it may not be important to you, I just want you to know there is the option.
Ken