It's a relatively old OP but here are my thoughts as a person on a bike.....
First of all, I think it may well depend on your route. A Camino like the VdlP may seem quite solitary to a walker. A biker can get to civilisation quicker.
Secondly, you ask if it's more of a cycling holiday and perhaps, less of a pilgrimage? In my experience that is up to you. A bike tour is a very different animal to a pilgrimage and I think it's helpful to decide which you are seeking before turning a pedal.
In my case I made it both, cycling from my front door in the Netherlands and back again. My time on the
Camino Frances was very, very different to my time before and after. I enjoyed both but for different reasons. If it's a bike tour experience you are after there are wonderful roads in Spain, fantastic diversity and no need to stick to a pilgrimage route.
There is definitely the lack of immersion in the Camino family but that's not to say there are no connections, just that they are typically shorter. Having said that, there are no rules and you can always adjust your pace. And there are other bikers too whose pace may be more suitable.
A real factor, I believe, is the time that we have. Someone looking to do 100km + per day won't have the time compared to someone doing 50km or 30km.
However, a bike can increase our range and allow us to explore more than the typical foot based pilgrim or just give us more time to stop and smell the roses.
A disadvantage that I found wanting to follow the walker's path as much as possible was that I often postponed my departure over several cups of coffee to allow the walkers spread out. Or sometimes I took the road, doubled back and then followed the walkers.
The last 100km from Sarria was very congested so I took to riding in the afternoon. By contrast, that first morning in St. Jean was a wonderful experience watching all the walkers head off, the majority on day 1. The excitement in the air was palpable, so much so, in fact that I abandoned my plan to take the road and instead joined them, often dragging and even carrying the bike.
I didn't regret taking the bike, although in my case with a bad knee walking was highly unlikely to be successful.
I was surprised when I realised that I had had a "Spiritual" experience along the Camino. I don't believe that I "missed out" on anything that the Camino had to offer, but then again we are all different and expect different things. Had I missed out there are services in Santiago that offer to help us locate what we are missing - or so said the card thrust in my hand in front of the Cathedral.
Whatever option you choose, I have found that it is helpful to commit to it and not be wondering if the other "way" would have been better. Second guessing ourselves is the way to madness!
Buen Camino
PS. Your inspiration appear to be books from the 80s. Spain and the Caminos have changed significantly in the time since then.