I think the answer is yes and the moves by most of the software 'only' manufacturers to add hardware lines proves that.
I am not convinced how competitive those companies can be, especially since they are not hardware specialists and most are buying in small quantities.
Overall, the VMS market has become very boring and not simply because no one is doing anything major but because there is not much more to be done (save for VSaaS which continues to be a disaster in the professional market).
I do not buy into the OP's premise.
I get 'why' software-only VMS providers would want to offer 'end-to-end' solutions, but how can one company be expected to 'be the best' at everything?
"I am not convinced how competitive those companies can be, especially since they are not hardware specialists and most are buying in small quantities."
I agree with that statement.
And to add to that thought, I think that companies who do try to 'do it all' (i.e. not focusing on what they do 'best') generally end up with a suite of mediocre products. Nobody can be an expert at everything, so why try?
An open-platform, software-only provider can focus on what they do best (and ways to do it better, stonger, faster) - and rely on their technical partners who already do what they do best).
So - rather than trying to engineer kick-ass products across the entire spectrum, the software-only provider can focus on engineering their software to integrate with those 'other things' - which increases the strength of the software-only product (and the scope of what their software can do) - rather than trying to increase that value by offering heterogeneous components.