Thank you for the very interesting read!
Just to clarify, as was mentioned a few times in this forum and on twitter, there is no preferential treatment given to any builder by the Titan Relay. The requirements for the websocket access are there to ensure fairness to any builder submitting blocks to the relay. The reason is very simple, as you mentioned bidding has become extremely competitive and any builder who has access to other bids without having to reveal its own is at an advantage. Having a quick look at the last 7d, there are around 10 builders which would qualify for access, assuming they were willing to submit most blocks and post at least 0.1 ETH of collateral.
Would also note that the distribution shown in Figure 7 is simply a function of the wider builder market share dynamics, looking at the last 7d we see how rsync has a 40% share at the Titan Relay over the past week.