It certainly does help manifest! I mean when you are filled with a lot of life energy, manifestation is easier.
I knew Jon Peniel briefly before he passed (I think in 2003?) through his wife’s niece, and she seemed to use it mainly for manifestation (we were both young and manifestation was the most important thing then). It is also part of many Qigong systems - especially in the Daoist Smiling exercise - where one can use specific emotions or intent to “ride” this energy wave after practicing it for a good amount of time.
Note that Left hand is Yin (for right-handed folks) while Heavenly Qi can be more Yang - and this posture is not random, it is accomplishing a lot of complex polarity balancing alchemy albeit it looks deceitfully simple.
The energy flow (heaven to earth) can also be reversed for some specific reasons, but I will not go into it here as it is not needed by most.