ASCE p62 "These modifiers [darkness] are negated if the attacking unit is a BattleMech or has the Searchlight (SRCH) special ability"
Listing SRCH for BattleMechs would be redundant.
Quick Strike cards had SRCH, SOA, SEAL, ES for all BattleMechs. I can't remember if we switched to dropping the redundancy with the change to Alpha Strike, or if it was a while later, but it was long before Commander's Edition.