This would certainly be suggested by the two facts that a) continuous enemy fire reduces the percentages at a steady rate, not an accelerating one and b) the severity of hull damage suffered in shields-up hits is seemingly independent of the percentages.
It's only when shields "collapse", as in ST6, that hits suddenly begin to pierce the hull unopposed. Powerful hits against minimal shields collapse the shields first and only then hit the ship in e.g. "Q Who?". I don't recall any blatant counterexamples at the moment...
Apparently, it's very difficult to damage the shields, that is, to do damage to the shield machinery. Rather, one only manages to drain the shields, but if firing ceases, the shields tend to recharge fairly quickly if there is power available. Thus, "regenerative" might be a general description of all Starfleet shields as they have behaved like this ever since TOS. Or then the same evidence could be used to support the argument that "regenerative" must refer to something else than the simple ubiquitous ability to regenerate, in which case the analogy to regenerative brakes begins to sound pretty good.
i agree with your explanation to a point I would say.
You're right that with each hit from enemy fire weakens the shield "recharge" rate depending on the amount of enemy fire incoming.
Here is my proposal for the difference between standard "rechargable" shields and "regenerative shields".
Recharchable shields simply means that, as always, the shield generators themselves recharge if enough power is available, or if the incoming energy from the weapons don't exceed the ratio of recharge/incoming fire. The recharging capability happens from the existing fusion, M/AM warp reaction, and eps tap combo's, so it's using the "intra-net" of energy creation to recharge.
ReGENERATIVE shields have the same idea behind them, but operate differently. Instead of taking incoming fire and using a recharge/uncoming fire ratio, and instead of using the existing intra-net of power/energy created by the ship, the shield generators and shield grids absoarb incoming fire using the radiation to directly charge the shield generators. This has the effect of regenerating the shields directly, so really it's incoming energy, then the energy is converted through the shield generators, and redirected to the shield grid to strengthen shields.
In the case of regenerative shield technology, instead of the generators operating with the ratio of recharge/incoming fire, they operate on a ratio of regenerate/incoming fire/bleed off. Meaning, incoming fire recharges then regenerates the shields directly, but too much incoming fire reduces the efficiency of the shield regeneration because the shield grid has to be used to bleed off excess energy/radiation. Because of that, the entire shield grid (or grids) aren't being totally regenerated, and the more incoming fire the less regeneration happens until the regenerate/incoming fire/bleed off ratio works in your enemies favor. Also, absorbing too much incoming fire and converting it runs the risk of overloading the EPS taps, then consequently much more important systems.
To me, that's the difference between standard rechargable shield technology, and the newer regenerative shielding technology. The regenerating ability is simply taking the older rechargable tech to the next step while still incorporating the original concept. Hey, it's better than creating an entirely new concept right?