Yes. The free version gets a lower priority when connecting to the VPN server. Not just that, the performance is not at par with the pro version. You are required to watch advertisements from time to time.
Usually, if your usage is limited in terms of time, the limit will not affect much.
The premium version offers:
Option to select any server from a list of 50+ VPN super fast premium servers in 15+ countries to connect to.
Better experience using the app without any advertisements or nags from free server sponsors!
Unlimited bandwidth & VPN session length - no restriction on session length.
Reduced Network Latency, resulting in optimized internet browsing even on the VPN.
So, no such limit as is in the free version!