No 5 Hit Light Combo?

Im using Luke Cage in AQ and i know he gains attack rating for debuffs so im parrying and immediately start light attacks and realized i can only dish out 4 light attacks in a row and thats the end of the combo. Was this always intentional or is this a minor bug?
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Comments
seems these are supported and valid combos ...
MM
MLM
MLLM
MLLLM
MLLLL
MLML
LLLL
.... etc ...
LMLLL
LLMLL
LLMLM
LLLMM
LLLL
All valid as well. Starting with a light helps with tenacity users and slows down sentinel(s)
MLML won't work, the second M ends the combo.