Hi ,
My recommendation is to check compatibility of Hinemos with vCenter 7. Much of the architecture has changed of vCenter 7 comparing to vCenter 6.x.
If you have previous version of vCenter with external PSC, Then it makes sense to have small size vcenter.log file as it is not running PSC related services and hence size would be smaller.
With vCenter 7.x, If you have converged your external PSC to embedded then size of the file would be larger than before. Just a thought.
As mentioned, do check with vendor on what they say about this behavior.