It isn't supposed to be different, rather its a whole new form of SSJ2!.
This form of SSJ2 is the merged transformation of SSJ2 of Caulifla + LSSJ2 Kale. Though we know Kale's LSSJ2 isn't official, I rather am reffering to their fused SSJ2 form.
This is evident that when 2 person fuse either by potara rings or Fusion Dance, they either use a transformation that both fused person have attained
or they either attain a new form in the fusion state(which is applied to Kefla's case) where the both persons gain this new form.
Gogeta's SSB = Goku SSB + VEGITA SSB(POWER IS NOT SAME,BUT I AM TRYING TO SAY GOGETA'S SSB IS RESULT OF FUSION OF GOKU'S SSB +VEGETA'S SSB + ADDED FUSION POWER)(ALSO NOTE THAT BOTH GOKU AND VEGETA HAVE ACTAULLY MASTERED SSB)
Now lets see kefla's case:
Kale already had mastery over her LSSJ, and caulifla had mastery over SSJ2,
so their fusion first gave rise to "KEFLA", then this "KEFLA" attained "LSSJ"(Legendary Super Saiyan) and then "KEFLA" attained "LSSJ2"(Legendary Super Saiyan 2/LSSJ who have ascended past LSSJ) as the new form of commbination of LSSJ with SSJ2.
Now u can notice the difference in the hair of Kefla SSJ and Kefla SSJ2 or rather Kefla's LSSJ and Kefla's LSSJ2!
THANKS FOR HEARING ME!