The argument is; assuming the metaverse economy takes off, its adoption could mean a huge number of people and businesses being connected to it, both financial and non financial. Buying and selling digital assets like #NFT in exchange for crypto assets (currencies).
As all these elements are highly volatile, a relatively big size of the metaverse economy with limited regulatory grip could mean a slight deviation in the perception of certain digital assets will have an impact on the entire ecosystem impacting a wider set of individuals and businesses.
Even though, metaverse is still being defined and these are just theories and maybe the ecosystem finds better ways of coping up with such systemic shocks, nevertheless I think it is a very relevant argument.