I forgot that it currently doesn't handle refugees right, this is not a bug, sorry everyone.
I was generating pocket worlds to check out the Age of Death (no sentients left), and got a really weird history bug.
First, while generating, the dwarven fortress appears as ruins, but it still is Age of Dwarves. world_sites_and_pops.txt doesn't show any dwarves at all. History shows that there are dwarves still living and breeding. Once the world is generated, embark screen shows fortress as a fortress and not a ruin. The dwarves are physically present in the fortress, with king and everyone.
Checking history, it seems to be a real mess. The dwarves were at war with goblins, lost, got the fortress destroyed and fled somewhere, but the war was still ongoing. Later goblins were exterminated by wildlife and Demonic Age ended, and with it the war. Historical maps don't show a dwarf civ after the destruction of the fortress and site history doesn't mention them either.
Created in DF v0.28.181.39e.
[WORLD_GEN]
[TITLE:POCKET HOLOCAUST]
[SEED:3802175575]
[HISTORY_SEED:2360545213]
[NAME_SEED:2504979612]
[DIM:17:17]
[END_YEAR:1050]
[BEAST_END_YEAR:1050:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:52:52]
[RAINFALL:0:100:26:26]
[TEMPERATURE:25:75:26:26]
[DRAINAGE:0:100:26:26]
[VOLCANISM:30:100:26:26]
[SAVAGERY:50:100:26:26]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:2:1:1:1:1:1000]
[GOOD_SQ_COUNTS:0:0:0]
[EVIL_SQ_COUNTS:0:4:8]
[PEAK_NUMBER_MIN:1]
[OCEAN_EDGE_MIN:1]
[VOLCANO_MIN:10]
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:0:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:250]
[RIVER_MINS:1:1]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVE_MIN_SIZE:500]
[CAVE_MAX_SIZE:500]
[MOUNTAIN_CAVE_MIN:15]
[NON_MOUNTAIN_CAVE_MIN:30]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_RIVER:2]
[SHOW_EMBARK_POOL:2]
[SHOW_EMBARK_M_POOL:2]
[SHOW_EMBARK_M_PIPE:2]
[SHOW_EMBARK_CHASM:2]
[SHOW_EMBARK_PIT:2]
[SHOW_EMBARK_OTHER:2]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:2]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:36:72:36]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]