If a third party cannot be considered the sole holder, those who store it with a third party, a buyer can say so and admit that he is the holder, but on the other hand, it cannot be said that if the trusted third party goes bankrupt and the liquidity of bitcoin is lost due to fraud or anything else, then you will only laugh with tears because you claim to hold bitcoin, when in fact you only entrust it without owning it.

Bitcoin stored with a third party is just a number; the actual Bitcoin is held and owned by them, not you.