PetrVlk, citing ME3 or ME5 as a licensing option is just that...one option. There are lots of other licensing options for customers. For example, customers that sign agreements under Enterprise/Enterprise Subscription/Server and Cloud Enrollments (EA/EAS/SCE) can purchase any of these Exchange Online plans to qualify: Exchange Online Plan 1/1G/2/2A/2G. This is documented in the Microsoft Product Terms.
And as those terms further state, if you want the additional functionality associated with the Enterprise CAL (like DLP, EOP, etc.), then you have to purchase licenses under one of these plans: Exchange Online Plan 2/2A/2G.
I agree that partners and account teams shouldn't be needed for simple licensing questions. The reality, this is much simpler than it might appear. We're making one, and only one, licensing change in the Subscription Edition products: we're no longer allowing the purchase of only perpetual licenses (we call those License-only or L-only for short). Simply put, we're not allowing L-only sales anymore. That is literally the only license change that is happening. I hope this clarifies things.