In my experience with hybrid rockets, the igniter is always triggered prior to or concurrent with the oxidizer flow into the chamber (which already has fuel in it, hopefully lit). This is to prevent igniting a chamber full of both propellants instantaneously - i.e., hard-starting the engine.
However, I also know that at least a couple of engines currently in use have a LOX-lead ignition sequence, specifically in order to prevent a hard start. I can't find a public source on this at the moment; any help there would be appreciated. I also welcome the possibility that I'm misinformed. The explanation I've generally heard is that LOX-lead prevents a hard start or 'detonation' of the propellants.
Sutton (9th edition) notes in Chapter 8.6, "it is difficult to exactly synchronize the fuel and oxidizer feed systems so that propellants reach the chamber simultaneously from all injection holes or spray elements. Frequently, more reliable ignitions are assured when one of the propellants is intentionally made to reach the chamber first. For example, for fuel-rich starting mixtures the fuel is admitted first." He also mentions this AIAA paper (98-3204) but it's paywalled and I'm not that frustrated yet. Chapter 11.4 of Sutton also replicates the sequencing summary of the RS-25 startup linked here.
I've had a hard time articulating the question so I'll pose it in multiple parts, and hope that's ok since it should just be a singular answer. What is the mechanism by which too much of an ox or fuel lead would cause hard start or 'detonation'? Aside from the 'fuel lead for fuel-rich' method Sutton mentions, how is it decided what the sequence for an engine will be? Am I misinformed about LOX-lead in modern engines, or is Sutton's above rule not universal?