That procedure is used after the loss of thrust near the ground (Sullenberger scenario) and it is recommended to use FLAP 2. (No VAPP in FMGC for F2)
The Forced Landing & Ditching checklist asks for Maximum Avail Flap (F3 or Full).
EMER LANDING ALL ENG FAIL and FORCED LANDING are two separate procedures. If you're doing a forced landing on a non standard airfield or a strip with engines available like due to smoke, fire etc. obviously you should land with Max flaps available to get minimum Vapp. That is available in the MCDU and as VLS on the PFD. But things are different when you forced land due to Double Engine Flame out. Double Engine Flame Out also puts you in dual hydraulic fail G+Y and EMER ELEC Config. That leaves you with flaps jammed. There is no great virtue in landing in Flap2 but since flaps are jammed, slat 2 is the optimum position that can be used. Slat 2&3 is same and slat full will further aggravate the already high attitude. Also no abnormal landings are done in Flap Full. FMGC1 is available but the MCDU approach speed is incorrect and will need amendment. So readymade approach speed is provided which is higher by appx. 20kts than the normal Flap2 speed. That's why the approach speed table is given. However in case of dual engine flame out if you manage to start the APU you will get out of EMER ELEC. In that case you can put the Yellow Elec pump on to get flaps and it is possible to do approach in flaps3. That will lower the approach speed and also landing distance which may be helpful if landing with insufficient field length. But the procedure doesn't mention that.