I can't confirm generating when in spectator or creative mode, like previous commenter said.
I tried using the locate command, teleported to the location, set gamemode to spectator (tried creative aswell), stopped the server, deleted the file containing the chunk in world/region folder to force the chunk to regenerate, started the server and logged in again. The chunk regenerated but there was still no stronghold generated. I deleted the right file. Structures I set up there for testing successful deletion got deleted as well.
1.13-pre2
Seed: -9193889702175967349
Location generated by locate command: -1832, ~ , 1176
I checked again in a newly generated singleplayer world in 1.13-pre6 and can confirm there is a Stronghold room but most parts of the stronghold are missing.