I might be different to a few people but generally; at least while I'm reading, multiple independent volumes is off-putting slightly to me. It requires the author properly linking, ordering things, it can clog up whatever reading list I put 10+ different 'novels' in, since they aren't all the same entity.
A new thing to add to my reading list, at least in my head, implies it could be stand alone, unless you intentionally mark volume 2 well as 'read the first volume' you have to start over with a lot of your expectations expecting new audiences who join at that point. The system showing your novel is also likely to lose traction for the first novel, I also would assume statistics start working against you as you then split any extra views/readers you might have had, into a new category.
Separating them might help for art and a whole list of things, and if done well it can help, especially when theres larger gaps between each main volume and a list of other things, but I can't help but wonder if it impacts the overall traction of the novel series.
Following the rule of web design, the more a person has to click to get where they want, the less clickthrough you will get. If a person has to click volume 8 and then locate volume 1, and then click on read among other actions, it could potentially be off-putting or otherwise detrimental to longevity but I'd love to know if theres data from an author who has done both.
Theres also a long conversation about potential fatigue if a new novel can pop up from nowhere, you are adding the expectation to readers to keep up to date, while many might have filed away the finished volume and never see the new post to check out the next volume, especially if they deal with a lot of things in their reading list. For the most part I wouldn't expect every reader to constantly check through their 'completed' list to see a new update about some new volume you have suddenly decided to write, and if the story leads straight into the next chapter, I'd question why it needed to be so separate then in the first place.