I had an interesting insight into both bumping fish and striking a few years back watching dad on a stretch of the Colne that was full of Barbel and Chub back in the day, after the first few weeks of the season the river used to drop gin clear making the famous 'aquarium' swims and you couldn't get away with two anglers in the same spot. With that in mind we'd take it in turns catching fish, even dad used to trott back then and it was cool to watch the float go down the swim, even if I was itching to get back in there myself.
The thing is watching the fish, his bait and his float from my vantage point downstream was an eye opener. Many a time i'd say strike when a fish clearly took the bait and he'd retort sharply with "At What ?" adamant that the float hadn't gone under, swapping places I too would suffer this and it was clear the fish, both barbel and chub were taking the bait and not even moving the float. Trying to counter this we agreed that if one said "Strike" the other would regardless of what happened with the float. Did it work? Basically no, we just ended up bumping fish off a lot and probably raising our voices a bit too much, looking back it was funny but there were lessons to be learnt.
Bottom line was the fish were ejecting the bait before there was time to strike, the bump off was either from the 'spit out' or a slight foul hook as the fish turned away, what was revealing was how slow we both were when the fish were really shy
We reverted to normal fishing next time with me just watching him and unsurprisingly the fish fed better without us hollering at each other, watching dad's float and the fish it was evident that when the fish were up for it they were more or less hooking themselves against what was a quite a crude float, often a barbel would be one metre sometimes even two away from where it took the bait by the time dad struck, he basically could have just held the rod still. The chub were more canny especially if the water was clear but they too would slip up eventually, and be well away with the bait before he struck. It was also amazing how much action was going on down there despite only tiny bites showing at times. It's worth adding that the fish that were taking freebies didn't bolt at all, only the ones that either felt the hook or some resistance
Nowadays this sight is commonplace for me on a gin clear River Lea and a few other rivers and it's not just on the lead where you get the three foot twitch, a loss of attention can often see the float heading off at a rate of knots before the Barbel finally spits it out, and sometimes you'll get lucky with a self hooker. The older wiser Chub, can be real cagey when it's clear and you can even watch them grab a maggot and even a grain of hemp between the lips so delicately, like they were using tweezers. Turning their noses up at anything big or unnatural. It's a mistake to think tiny bites are small fish. Other times the chub can just be bonkers and hit anything that moves therefore it would be a mistake to be judging what a fish does on the good days, bump offs rarely happen when it's one after the other. This is replicated with the other species and often the only way to get a good ratio of fish per strike when things are hard is by freelining a visible bait, bump offs are extremely rare when doing this but obviously it helps to be able to see the bait. Watching the line move on the suface if you can't see a bait is a really clean way of fishing and bump offs don't happen doing this either.
I'm of the belief as a float angler that a lot of my fish are semi hooking themselves. Controversial thought maybe but visualise a bait on a float down the end of a swim, how far is a feeding fish going to take that before the float dips? when you consider the angle from rod tip to float to hook, even held back hard there's a lot of movement for that line to make before the float goes under. Bump offs therefore are unavoidable unless you have the fish hooking themselves against a heavy float, the quicker you strike maybe the more you'll suffer bumps, but you will still end up hooking some of those quick bites, or those really shy bites come winter, some of my biggest fish have been the tinest of bites on really cold days but how far they are actually taking the bait i'll never know.