Yes. The inverse + sync is required in order to combine both outputs to double the voltage potential (boost) on all models of the boost (v1 - v3.1).
If you use Follow Out 1 which does not invert Out 2, then the two signals will cancel out when processed by the boost.
Of course, you can still elect to not use inverse + sync, in order to combine two separate distinct outputs into a single output connection.
For more details, please check the link: