An EV is a specific point on a scale, not a range.
The film we are metering for defines the range. When we set the EI/ISO on the meter we are telling the meter the offset from the measured speed point of the film to the light measurement done by the meter. The ISO standard defines one way of finding the speed, there are many others that have been described by various and sundry sources. We can apply all kinds of factors into the EI number for any reason we please.
The 5 stop range thing is an urban legend, a myth, some body's over simplification.