Or a LAN. Could do a WAN which itself can be interconnected over a wide area. Usually by routing over the internet but you could use something like satellite uplink or miles of dedicated cables.
But the interconnection of multiple LANS and WANS is what would make an “internet”.
So maybe 2 universities joining their own networks would be moving towards a private “internet” but I think we’d still call that a private network or a WAN.
It’s interesting to consider where the definitions change.
If a person is at the intro/intermediate level that advice may be sound enough. Since they’re less likely to apply proper rules to include those ranges of IP’s etc.
Assuming it’s advising disabling it at the router/switch level and not just a per device level.
Better would be to explain: Disable this until you’re familiar with the following concepts (see cited books/material for more info)