GET /v3/api-docs/accounts-v1   -> operationId=getAccountV1, schema=#/components/schemas/AccountV1, params=[id]
GET /v3/api-docs/accounts-v1.1 -> operationId=getAccountV1Point1Plus, schema=#/components/schemas/AccountV1Point1, params=[id]
GET /v3/api-docs/accounts-v2   -> operationId=getAccountV2, schema=#/components/schemas/AccountV2, params=[id]

Each group's VersionedOpenApiConfig#collapseToSingleVersion customizer rewrites the same
merged oneOf operation shown in 02-what-springdoc-actually-generates.txt down to exactly
one schema and drops the now-meaningless API-Version header — the default (ungrouped)
/v3/api-docs document is completely unaffected, confirmed by re-fetching it below:

200
{"openapi":"3.1.0","info":{"title":"OpenAPI definition","version":"v0"},"servers":[{"url":"http://localhost:36991","description":"Generated server url"}],"paths":{"/accounts/{id}":{"get":{"tags":["account-controller"],"operationId":"getAccountV2","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string"}},{"name":"API-Version","in":"header","schema":{"type":"string","default":"1.0.0","enum":["2","1","1.0.0","1.1"]}}],"responses":{"200":{"description":"OK","content":{"*/*":{"schema":{"oneOf":[{"$ref":"#/components/schemas/AccountV1"},{"$ref":"#/components/schemas/AccountV2"},{"$ref":"#/components/schemas/AccountV1Point1"}]}}}}}}},"/widgets/{id}":{"get":{"tags":["widget-handler"],"operationId":"getWidgetV1","responses":{"200":{"description":"OK","content":{"*/*":{"schema":{"$ref":"#/components/schemas/ServerResponse"}}}}}}}},"components":{"schemas":{"AccountV2":{"type":"object","description":"Account shape served by API version 2 — restructured, nested contact object","properties":{"accountId":{"type":"string","description":"Account identifier"},"displayName":{"type":"string","description":"Account holder display name"},"contact":{"$ref":"#/components/schemas/Contact","description":"Nested contact details, replacing the flat email field from 1.1"},"status":{"type":"string","description":"Lifecycle status, new in v2","enum":["ACTIVE","SUSPENDED","CLOSED"]},"apiVersion":{"type":"string","description":"Echoes the resolved API version"}}},"Contact":{"type":"object","description":"Contact details nested under an account, v2+","properties":{"email":{"type":"string","description":"Contact email"}}},"AccountV1":{"type":"object","description":"Account shape served by API version 1","properties":{"id":{"type":"string","description":"Account identifier"},"name":{"type":"string","description":"Account holder name"},"apiVersion":{"type":"string","description":"Echoes the resolved API version"}}},"AccountV1Point1":{"type":"object","description":"Account shape served from API version 1.1 onward (baseline handler)","properties":{"id":{"type":"string","description":"Account identifier"},"name":{"type":"string","description":"Account holder name"},"email":{"type":"string","description":"Contact email, added in 1.1"},"apiVersion":{"type":"string","description":"Echoes the resolved API version"}}},"ServerResponse":{}}}}