It's easy to get a bit tangled up with this. Points of relevance (and some have been made by others, above) -
(a) the 400ft thing is tied up with AFM OEI profiles and is a consequence of the heavy design Standards
(b) for a given runway, the operator may schedule some higher third segment for terrain optimisation or whatever. In this case, read the higher figure instead of 400ft. It is noted that the maximum retraction height, OEI, usually will be based on either engine operation at rated thrust or some other systems limitation (eg RR Dart powered Types at 600ft - although, just at the moment, I can't bring to mind what the system limit was - autofeather time limit, perhaps ?)
(c) the operator will (should ?) do the sums to make sure that the presumed/declared OEI escape path achieves the usual obstacle clearances
(d) for SID style departures, the AEO case is subject to additional climb/obstacle clearance considerations
(e) providing one respects (c), by operating in a manner that keeps the aircraft above (generally, well above, in practice) the OEI net profile, and (d), for similar considerations, there is nothing, per se, precluding your using a different flap retraction profile for routine AEO departures. Indeed, such is seen in just about every operations manual dotted around the paddock.
(f) one notes that many, if not all, operators, use a standardised departure profile, typically based on the critical runway for the particular operation. This makes a lot of sense for flight standardisation purposes.