The 400' referred to should be used for two things:
- The earliest opportunity to turn has been identified aurally by non flying pilot (PNF) to the pilot flying (PF);
- In case of no emergency turn, the point at which the PF can call for what malfunction has occurred;
Then, subject to immediate turn considerations and workload, the PF can ask for any memory items / recall actions to be completed by non-flying pilot (PNF). These may include the PF actioning some thrust levers, acknowledging the right engine and memory item to be completed, so for that reason any turn distractions at that point are totally distracting.
A turn may only be required after some distance, in which case it would make sense to complete these actions on the straight climb out part. If an immediate turn is required, this has absolute priority, and the 400' call could be an identifier to turn, so the call for stating malfunction can wait until turn completion.
Once turns have been completed, aircraft is accelerated to flaps up manoeuvring speed, crew have obeyed the thrust limitation (e.g. 5 or 10 minutes subject to operator and type variation) in the manoeuvring process, it's time to do any additional checklist items.