When people say "hold bitcoin," they mean that you should not sell or spend it quickly because they believe that the value of bitcoin will increase significantly in the future. If you look at the history of bitcoin, you can see that it has increased significantly over time, although its price can be very volatile (it can go up or down a lot at once).

If someone owns $300,000 worth of bitcoin, whether they should spend it now or wait depends on their risk appetite, their belief in the future value of bitcoin, and their financial needs.
If they believe that the price will increase further in the future and they do not need the money urgently now, then holding on for a while may be a good idea.

But if someone feels that they do not want to take the risk or need the money now, it may be reasonable to spend it.