I think the ATO's position here is.... questionable... to put it politely. It also directly affects me, so I will have a dig into this. I am yet to find a good source of the ATO's position where they actually argue it with, you know, facts and legislation and court cases, etc.
To me, the key issue appears to be whether or not BTC is seen as a fungible asset. Assuming you don't believe in things like 'rare sats', then it just is. There can only be a change in beneficial ownership under the conditions suggested in the ATO's position if each sat is not just like every other sat. I can't see a reasonable way to argue that beneficial ownership has changed, unless you're speaking about specific sats, and I think talk of sats being anything other than fungible is just pure fantasy.
Let's draw a parallel with the question regarding depositing and withdrawing BTC from exchanges potentially being a CGT event. If I have some gold coins and deposit those into custody somewhere, do I have to be promised at the outset that the exact same gold coins will be returned to me in order for there to be no CGT event? What if my commodity of choice is rice? Or oil? How about natural gas? I don't know the answers to these questions, but you can see how silly the concept gets if you follow it through to its logical completion. I would be very surprised if other commodities were being treated the same as the ATO is suggesting BTC should be treated here.
Anyway, I will have a dig into it.
If I decide I am right, the next question will be what to do about it in a practical sense.
I am currently using one of the other lending platforms you mentioned, and there are significant difficulties around their end of loan process as to why I wouldn't recommend them. As I come from a real estate background, I sort of assumed that I would be able to sell the collateral asset in order to pay back the loan at 'settlement'. However, the platform in question have told me that their base case is that a loan paid out in USDC will be paid back in USDC BEFORE collateral is released. I am not sure how they think that works in the real world, but we have a few months before it becomes an urgent issue, and they tell me they are actively working on alternatives at the moment.