Sure thats a fair point...
I was just answering the "who pays" aspect, and before that the "why" aspect, and as I think I have shown the who and why and how are actually, upon looking , quite obvious.
The "who pays" question raises exactly this point. When those performing the security are monolithic in nature (either explicitly or by implication), you might as well use a private database.
Well the who pays , as stated in this case, are the multiple actors that will use the system.... firstly the HMLR themselves, then the actors that they interact with, and ultimately the paying clients that they serve, what they are doing is streamlining and decentralising the process somewhat , and moving away from a completely centralised , slow, leaky, fraud prone, expensive, manpower hungry, system.
Also, the network, the private permissioned need to know only , network, that they are building, which will be supported by nodes, it will live on the R3 Corda "blockchain" which is really a DL.... which is then secured and maintained in its own right (and not maintained by the HMLR)
Is the Corda r3 DLT anything other than a DL, that allows for "decentralised databases" , no.
It (corda) is not a permissionless network, it is nothing like BTC, it is not trying to be.
But it is precisely because they (HMLR) need to have a non fully centralised system in place to achieve what they are trying to achieve that they have chosen to explore this route... and it is specifically a "private enterprise "blockchain"" they have decided to explore, on a permissioned distributed ledger, because, the actors involved are carrying out private transactions, which are on a need to know basis only , which require immediate atomic, deterministic immutable settlement. Also worth noting, that due to the nature of the real estate transactions they will be recording, they have chosen a structure which will have legal standing which Corda provides.
So they have decided that they certainly do not want to use a permisionless public blockchain, which indeed would perhaps be unsuitable for what they are trying to achieve.
Yes, it is mundane, its not that revolutionary.. it ain't "property NFT's" , it ain't a fully decentralised public blockchain solution...
I still find it interesting...