Hello Bhawandeep
I tried labbing this up and indeed, on Cisco’s CML, if the EIGRP process is up by default. You don’t need to issue the no shutdown command. I suspected that this has more to do with EIGRP named mode rather than with EIGRP in IPv6, so I tried labbing named mode up, and on CML I still found that the EIGRP process is up and running by default.
I even found Cisco documentation that states that in named mode, the EIGRP process is down by default and you must issue the no shutdown command. 
In any case, it’s good to keep in mind that these defaults are not always implemented in the same way on all platforms, so keep an eye out for such discrepancies.
I hope this has been helpful!
Laz