`engine_forkchoiceUpdatedV1`/`V2`/`V3` allow beginning payload build process if `forkchoiceState.headBlockHash` references a `VALID` ancestor of the head of canonical chain
https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/paris.md#specification-1 notes:
> 2. Client software **MAY** skip an update of the forkchoice state and **MUST NOT** begin a payload build process if `forkchoiceState.headBlockHash` references a `VALID` ancestor of the head of canonical chain, i.e. the ancestor passed [payload validation](#payload-validation) process and deemed `VALID`. In the case of such an event, client software **MUST** return `{payloadStatus: {status: VALID, latestValidHash: forkchoiceState.headBlockHash, validationError: null}, payloadId: null}`.

But
https://github.com/status-im/nimbus-eth1/blob/bda760f41dac22f66c9a3ffa56d25bd2f274f4d1/nimbus/beacon/api_handler/api_forkchoice.nim#L130-L136
combined with
https://github.com/status-im/nimbus-eth1/blob/bda760f41dac22f66c9a3ffa56d25bd2f274f4d1/nimbus/beacon/api_handler/api_forkchoice.nim#L188-L207

allow exactly this.