When spawning in a caves world type and using the /locate command to find a stronghold, you can't find any. I've tried finding a stronghold in 3 different worlds and have also used the command periodically while exploring all 3 worlds and all of them didn't have a stronghold. I also tried to check with eyes of ender just in case the /locate command wasn't working properly, however; it seems that eyes of ender are unable to be thrown in this world type so I couldn't find a stronghold with either method.