While it is not really "actual company shares" which is listed on the exchange, such tokens are "backed 1:1 to traditional stocks, entitling holders to the same economic benefits of owning the underlying stock."[2]
There is no timely, provable way of guaranteeing this 1:1 backing. That is the main concern.
Also, it seems like that this is really no different to CFD contracts that are offered by eToro and other trading platforms - they are not the actual asset itself but a derivative that will give you exposure to the underlying asset. Obviously, this could be great for some people but the counterparty risks are too immense for any long term investors to seriously tap into this field.
This is something that I have speculated for a long time. The merging of equity/bond and crypto exchanges will be inevitable, given the fact that the primary exchanges for these traditional fiat instruments are relatively inaccessible for retail investors.