Vodafone provides stronger network to their own customers / so sad

I realised that however Lebara uses Vodafone's network, Vodafone gives stronger signal to their own customers, which is not right. As much as I know when I used 1pMobile and with another sim EE (1pMobile's provider), they gave the same strength of signal to their own customers and to 1pMobile customers, so their cooperation in terms of signal strength for me looks more fair in terms if what Customers get (same strong network, same coverage).

Only me feeling like it is something to re-negotiate between Lebara UK and Vodafone UK?