@Sasha the simple answer would be that the highlighted text is not relevant to the current structure. The text in question (now under clause 13.10 b) is not newly introduced but has been preserved from the previous version of the Terms of Business. And most importantly, all client funds are always protected by us under CASS.
Further clarification on how the clause corresponds with the custody chain. 
The wording referred to by Sasha refers to a hypothetical situation where assets of clients of Trading 212 UK Ltd. are registered in the name of Trading 212 UK Ltd. As mentioned above, Client Assets are always protected by Trading 212 UK Ltd. under CASS 6. Due to the custody chain, it may be the case that assets are not recorded in your name but in our name, the name of our custodian or a sub-custodian down the chain. Currently it is the practice of our custodian and the custody chain we use to register assets in the name of the end sub-custodian or a third party nominated by that sub-custodian. This means that the current practice is that assets are not registered in the name of Trading 212 UK Ltd., therefore the provision referred by Sasha is currently not applicable. As mentioned above, for instance with US shares, the end custodian is the Depository Trust Company (DTC) in the US. The shares are held in the name of a third party, DTC’s nominee entity, Cede & Co, as standard in the US.
Trading 212 UK Ltd. always strives to provide widest possible access to the worldwide financial markets to you, our clients. It may be the case that certain overseas markets (for instance outside the most commonly used markets in the US, UK and EU) require or have a market practice that assets are recorded in the name of the end broker, this being Trading 212 UK Ltd. This is why this provision is part of our Share Dealing Terms of Business, even if not applicable currently. For the avoidance of doubt, at all times Trading 212 UK Ltd. will comply with the applicable rules under CASS 6 for the protection of your assets and you remain the beneficial owner of any shares.