Strongholds spawn in circles about the world origin. There are three within about 2k blocks, but then more further out. There are up to 128 strongholds per world.

Even with just the three, there is access to multiple spawners, and an extra end gate can simple be removed with mushrooms.

That said, Gravel is already renewable with the addition of Piglin trading, so this isn't particularly necessary. It does, however, give options.