Its essentially the same.
Even if you have a plane with 1m per vertex like the landscape, you need high multipliers to get to something decent.
At the core, every square can only be 2 tris or more.
And you likely still have to tile several tiles to get some credible water.
Loading in a single sheet means no culling.
No culling means less performance.
To get around that, you could use some distance based multiplying algorhytm somewhat, to lessen the cost of tessellation. But you still pay way too high an entry cost compared to a proper lod ready mesh used in conjunction to an HISM…
IN ue, at least, its always been more than prohibitive even when “done right”…