The discussion you linked (here) shows that both researchers agree that 'garbage enzymes' are mostly acetic acid or vinegar, with a low pH(3-4). Fresh papayas contain papain, but roughly 2% of the enzyme self-digests per day in aqueous solution. Bromelain from pineapples is still active at acidic pH. Like most other proteases, it self-digests much more rapidly than papain. As a result, any digestive enzymes present when the mixture was made would destroy themselves by the time the mixture matured.
((Those among you quick at math will note that perhaps 1/5 of the papain activity would remain after ninety days. While true, there's evidence yeast cultures eat gluten for sustenance, and if they can digest gluten they'll digest papain. There's no reason to expect yeast to leave a delicious protein source unused.))
If the solution acquired proteases somehow, they would self-digest under the conditions the 'garbage enzyme' solution is stored at(room temperature, aqueous solution, nothing exotic like formaldehyde, months). The yeast itself by the time the fermentation is complete has died, destroyed by the acetic acid(or ethanol, depending) they created. Any digestive enzymes used by the yeast to dissolve proteins destroy themselves as the mixture matures and the yeast die off.
If the mixture starts with no digestive enzymes, there's no mechanism to get appreciable amounts active digestive enzymes. If the mixture does start with digestive enzymes(papaya or pineapple), either the yeast will eat them and then die or they will digest themselves and the yeast will eat the byproducts. Finally, the yeast will die.
It's a vinegar/alcohol blend, depending on how much oxygen is available during the fermentation, and it smells like whatever you put in it. If you used orange peels, it probably smells pretty okay. That's why it cleans.
If you are anxious to use real live proteases, there are powdered papaya/pineapple/etc powders you could reconstitute in water right before use. They are usually sold as meat tenderizer among other things. There are also blends of enzymes sold for pet urine deodorizing, and general purpose cleaning fluid with bacterial and enzymatic action. Formulating those at home is going to be fairly involved, but if you wanted an enzymatic cleaner you made yourself that's how to do it.