Where I currently work, the SOP is NOT to specify the direction of evac. It's up to the Cabin Crew to assess whether a particular exit is safe to use or not...
The CC are 'on spot' for every exit, while the pilots sit up to 200 ft forward, so IMHO the CC are better suited to decide.
PLUS, while specifying direction, there's an added potential for left/right-hand confusion eg. for aft-facing CC's
Just to add
CC need a little help from up front knowing if an engine is running or has been shutdown on a side (in some cases)
Also I doubt there is much confusion between left or right when the CC talk about L1 vs L3 no matter which way they are facing. But as always there is increased opportunity for confusion between CC and passengers in the event of a fire.