In answer to the question, no, I don't think it damages the experience. In most cases, much like a TV show, it's giving us hints about what is to come and thus building up both our anticipation to see how these events will unfold, but also allowing us to think and to theorise about what will happen thus keeping us engaged.
It's only an issue when people forget that we are privy to much more information than the MC, like in the case of Quinn, that it becomes something of an issue when some people are assessing the MC's actions based on what we know and not what he knows. It's easy to judge the MC's action when you have all the information, but he doesn't, and people need to remember to separate those two things out when assessing and judging his actions.
Another issue can be when we see LIs being intimate with others because, even if it is something that has happened or is happening, it's not something most people want to see when they have an emotional investment in certain characters.
There are still lots of things we haven't seen and I don't expect DPC to spill every detail in these non-MC side scenes before the shock reveals, much like it was with the M&J reveal. So when it comes to someone like Bella, we'll get hints, teases, and maybe some parts of her story, but we'll still likely get blindsided by something that we didn't really see coming.