When Ancient Cities are generated in Java Edition, they use a single camp site structure which is neither the place-available camp_1, camp_2, or camp_3 structures. It is a mystery as to where this structure data is coming from.

Steps to reproduce:

Generate a new world and locate one or more Ancient Cities with camp site structures. See the Observed Results below for some examples seeds and coordinates.

Expected Results:

Using the /place template command, these are the results of specifying the camp_1, camp_2, and camp_3 structure files, respectively, and are what would be expected to be seen in any Ancient City with one or more camp sites:

Observed Results:

Seed -977118593:
X: -353 Y: -40 Z: 1378 (Two identical camp sites of unknown structure):

X: 367 Y: -45 Z: 1327 (This is near the previous screenshot; the other identical campsites in previous image can be seen in the background. This one is also identical and unknown.)

Seed 5305220127415150578 (20+ Ancient Cites around spawn; here are a few examples, all are consistently generating a single unknown camp site structure):

X: 163 Y: -45 Z: 122

X: 53 Y: -45 Z: 133

X: -306 Y: -45 Z: 542