Utility says the new substation is for a data center. Does that do anything for my land two miles away?

Powered land, used strictly, means a parcel with a documented right to a specific amount of electric capacity at a specific date, usually an executed electric service agreement with the utility or an interconnection agreement with the transmission operator. Loosely, brokers use it for anything near a big line, and that loose usage is where people lose money. Proximity to a substation is not capacity. Capacity is allocated, and once a campus has been promised the block, the substation can be full from your point of view even though it's a mile away.

What proximity does give you is a shorter and cheaper build for whoever wants to connect next, so your land can matter in a later phase if the utility adds capacity at that station. The question to ask the co-op, in writing, is how much load is already committed at the new substation and what the timeline is for any further capacity there. They may not answer in detail, but the answer you get tells you a lot.

The part people miss is water and fiber. Cooling needs a water source or a plan that avoids one, and the facility needs multiple fiber routes, so a parcel with power and no fiber path is worth much less than the power alone suggests. Also worth checking your county's zoning and any noise ordinance, because a campus next door can change what your acreage is good for either direction. And if you ever market the land yourself, whether that triggers a real estate license depends entirely on your state.