There are a number of ways to probe a data bus for the presence of a signal. You don't need a scope capable of fully characterizing it to know it's there. And

There are a number of ways to probe a data bus for the presence of a signal. You don't need a scope capable of fully characterizing it to know it's there. And furthermore it wasn't difficult or expensive to get ahold of a 10 year old scope in the 90's; it just took slightly more effort.