Uh, no. If it was "cash", or equivalent, it would be under "cash and cash equivalents". Marketable simply means they can be traded (IE they are not something like non-OTC stocks)

They may be long term instruments that they would take a loss on if they traded before maturity. Heck, they may be long term instruments that have trading restrictions on, etc.

It's simply not cash. Period.

If long term assets have trading restrictions they're not marketable. I get that it isn't cash cash in the most literate sense, it's liquid assets, which is nearly equivalent to cash, just like the "cash" in your bank account.