My 2020 boxer has both and yes as I said they are 2 separate systems that both help reduce emissionsI'm not too sure on this ..but Adblue and eolys systems are two different engine systems, they do not run together .. it's either - or.
The eolys system has a tank for deisel -fuel additive which is for reducing particles /cleaner burning.
The adblue is a tank for adding into the exhaust sytem to neutralise gas emmissions.
I googled and it seems Fiat changed from eolys to adblue around 2016.
I think if you using an adblue lock cap then removing the fuel cap is not going to confuse the eolys system because you won't have eolys and adblue together.
I'm pretty sure some more Funsters can help us and know the proper info.