The main reason I assume is scenario based. Say you do a JIP combo and the JIP,2,2 portion is blocked or just the JIP,2 is blocked. You would have possibly already hit 4 in preperation to cancel with clone at the end. The EN ice beam gives you a chance to quickly convert upon recognizing a hit of maybe the last 2 giving you a chance to get damage. So what was initially going to be a blocked JIP,2,2,4,ice clone could be converted into a hit 2,2,4,En ice beam. Thats my best guess, otherwise yea, Id never choose to purposely do this instead of a meterless combo.
Somberness thanks for sharing some frame math on this, the community would be lost without you.