I was thinking of VFR and that going up 2000ft to the next FL for your track in a situation of falling pressure in order to maintain terrain clearance is frequently not possible.
Yes that can be a problem not just for VFR flights but in the case of IFR flights operating in IMC, the position of the freezing level and icing layers can prevent flight 2000ft higher.
The UK only recomends that VFR flights follow the quadrantal and it is very good advice.
In other countries where VFR flights cruise according to the ICAO semicircular table of flight levels for VFR flights then one will often find that such a requrement only applies when more than a specified height above the terrain. 3000ft in some cases or in others "3000ft AMSL or 1000ft AGL whichever is the higher".
The ENR section of the appropriate AIP is the best place to start looking.
Regards,
DFC