LR2 and O2Jam operate very differently. In LR2, there is the Poor Judgement, which I believe is triggered when you press WAY too early. IIRC Poors reduce your life like a miss would, making spamming through difficult sections essentially impossible since you'd end up killing yourself by pressing keys that have notes coming up soon. In LR2, I believe LNs work similarly to stepmania (someone please correct me if I'm wrong). I think they require you to press in the beginning, but do not require lifting right at the end of the LN. I have no idea how releasing early works, or if repressing does anything in LR2, so someone who actually knows about LR2 will have to cover that.
In O2Jam, you can actually spam notes pretty well. The judgement windows are very lenient, so BMS style patterning (patterns with lots of notes, but not LNs) is pretty easy to spam. On the other hand, LNs in O2Jam are much harder than LR2 or o!m. Even though the timing windows are easier, in O2, you can't repress an LN. If you make any mistake on an LN it counts a miss immediately. On top of that, you are required to press the LN at the beginning, and release at the end, like in o!m, but with much stricter health when it comes to LNs. Missing hurts a lot, and holding LNs does not increase your health over time like in o!m. LN mechanics and the fact that starting around level 30, most charts have a fair bit of LNs, mean that anything with LNs requires you to play the LNs legit (IE not spam).
In short, both games have some element of the mechanic that makes it harder to spam through their charts, neither of which are present in osu!mania.