Vacant land liability is a real and fairly cheap product. It covers you if someone gets hurt on land you own, which is the actual exposure on an empty parcel. Trespassers on ATVs, a kid at that old two-track, a tree that falls onto the neighboring property. Your agent is right that there's no structure to insure, and the other agent is right that the structure isn't the risk. Pricing is usually low, often a couple hundred dollars a year for a policy that can cover several parcels under one schedule rather than one policy each, though what's available depends on the carrier and on your state.
Title insurance does something completely different. It protects against defects in the ownership record, an old unreleased mortgage, a missed heir, an easement nobody disclosed. When you sell a lot, the buyer gets an owner's policy covering their new parcel. That policy protects them, not you. Your own protection comes from the owner's policy you bought when you acquired the whole tract, and you'll want to confirm with the title company how that policy carries across the new lots once you record the plat, because practice on this varies.
The cost most people miss on a split isn't insurance at all, it's the tax bill. Once six new parcels hit the assessor's roll, each one gets its own assessment, and in a lot of counties the total on six lots is meaningfully higher than the total on one tract. If the parent tract was under an agricultural or timber classification, splitting it can also trigger a rollback of previously deferred taxes going back several years. That's state and county specific, so ask the assessor directly what happens to the classification when the plat records, before you file.
