They could, in theory, have logical equivalence. If my ISP retains neutrality wrt transport between YouTube and my client [eg to comply with legislation] they can _in_theory_ pay Mozilla instead to throttle the connection at the UA for any user with an IP on the ISPs network, delay transfer, limit total data, etc. - the effect would surely be close to identical to ISP interference wrt the traffic carried between YT and my client browser.
Because of the possibility of such an equivalence it strikes me that the issues are not _separate_, though obviously not identical either. If Firefox blocked/throttled sites but allowed others [in the same category] for money, then Mozilla through my client would be enacting the same effects as net non-neutrality. They could charge for an add-on to remove all/some blocks, or charge the server endpoint company to remove the block just for them.
The point is that for a user the important endpoint is their sensory input, and that a browser manufacture can filter/throttle/block that consumption in the way that an ISP can.
Legislation could be written that would encompass preventing a browser manufacturer from covertly interfering in data transfer, whilst equally demanding ISPs carry data regardless of origin. Equally poorly drafted legislation targeting ISPs could impact browser makers ability to implement black-/grey-/white-listing of malware, etc..
Whilst we're focussing on such bias that can interfere in our web/internet consumption I think it's the perfect time to make sure we don't solve the problem in one place only to leave a gaping hole that allows the same corporations to enact the same controls.