This is not, for the most part, true on modern phones that have a decently recent OS.

In any case, while this is a theoretically possible attack, it's insanely expensive. State-level operators might try something like this if they're trying to compromise a particular individual's phone, but common criminals are not going around renting hotel rooms one at a time and disassembling USB charging ports.

In any case, it's a bad idea to use these for phones, but mostly because most of these devices deliver a pathetically low amount of current.

I've used them to charge earbuds and other low-power devices but I always charge phones using something with more oomph.