There is a strict version. Power is secured when the utility and the site owner have an executed service or interconnection agreement that names a specific amount of capacity in megawatts, names the point where it will be delivered, and names a date it becomes available. That document, plus the money already committed to the utility for the upgrades, is what "secured" properly means.
The loose market usage covers everything short of that. A will-serve letter, sometimes called a load letter, is the utility saying it believes it can serve your load, which is not a commitment of capacity. A queue position is a place in line for a study. "Utility engaged" is not a defined term at all. So your two listings are describing different worlds. The one with an energization year attached to a phase is closer to the strict version, though I'd still want to see whether that date comes from a signed agreement or from the developer's own schedule.
The reason this matters more here than in most property types is that power is the binding constraint on supply across the whole sector. Grid capacity and delivery timelines, not tenant appetite, are what limit new facilities, which is why an existing site with power already flowing carries a premium.
One thing worth knowing early: capacity comes in two flavors people blur together. Contracted capacity is what the utility owes you. Critical load is what the tenant can actually plug in after cooling and losses. A site can honestly advertise 200MW of the first number and deliver much less of the second.