Correct. You can also run a 3-3-5 and put one of your backers on the line to rush much like Harrison did for Pittsburgh and you have a 3-3-5 that functions just like a 4-2-5. There are various options but what is constant is the 5 defensive backs which is the crucial part when defending the spread. Whether you play a 4-2 or a 3-3 isn't as important as having enough secondary defenders to cover all of the spread elements.
Yes I agree. I just edited my post above and noted TCUs use of 3 "safeties" where one is pretty much a lb. Bottomline is having length and speed all over the field.