what percent charge are you at when this happens?
typically it should not turn yellow on the normal software until you hit 40 percent, and i believe red was under 20 percent.
yes at 40 percent your overall power and accel is limited pretty well. one oddity i have seen is, from 40 to 30 it's kind of grannyish like you said, from 30 to 20, the bike won't take off like a demon but seems like it has much more accel than 30 to 40, which is odd considering. i can still overtake someone fairly well when in normal software which was surprising.
once you hit 20 percent, it will hit, i want to say like street mode 112 mph but the acceleration is very restricted, as you said it can be tedious overtaking someone. you will eventually get speed but not super hard accel. under 10 percent it's basically in granny mode, the bike is not trying to pass people, win races, in it's mind it's just trying to get you home, or at least until the next charging station. your speed is limited and your acceleration is very limited. Do not quote me on this i have not validated it yet but i think it's shooting for a voltage level... give him what you can but do not drop pack below xx volts. so it throttles and goes real easy on the battery trying to stretch it out as long as possible.
at that low of a power level, the battery chemistry is near it's end as well, and current really impress' a drag on it, instead of, lets say, being able to make 400 amps, the battery can now only make like 80 amps... yet it still takes the same amps to go xx speed. this will cause your battery voltage to sag very heavy , instead of maybe seeing a few volt sag, you may be seeing a 10 volt sag, because of the weakened chem. This makes things worse, the power is even less, so now it wants more amps, meaning more current etc... you will very easily get into the voltage cutout zone on the battery. When these batteries discharge, they have a small curve, that picks up in the like last 15 percent of discharge, then will fall off a cliff volt wise. so the volts will crash very easily and quickly when near the end.
the regen switching off, this seems counter intuitive, however i think is an artifact of the amp limiting in affect due to your low soc, it minimizes amp flow, it don't care which way. in reality unless you have heat issues you want those amps back in the battery. if the battery is at its last few percent though, you don't want to go slamming it, you want to walk it up a few percent then load it up with current, if something is going to go wrong, that's one of the places it will happen and being discharged that low and hitting it hard can be very harmful to them.
the racing software, you don't see any programmed power drop, but you will see the laws of physics kick in. If the battery is at 340 volts and you swing the throttle, it's taking off like a scalded cat and you better be holding on, if you are at 20 percent charge and it's now only at like 280 volts, well that's about 30 horse you lost there, so yes it's going to be slower to romp but don't let that fool you you better be holding on. of course your battery is also, less able to pump tons of amps, it may only max at 300 amps now, instead of the original 400 limit, so that is another 40 lost etc thing.
it's designed to win races, and is not going to restrict power except to prevent you from setting the battery on fire. Basically thermal is the only cap you got. it WILL of course not let you over discharge it either as that also is dangerous.
The road package is designed for longevity, to protect your battery, and to get you from point A to B. Another thing to keep in mind, an Energica stuck on the side of the road because you ran it dry is embarrassing too, they'll try to get you home! hence the last ditch walk mode etc

The short answer, i do see something sort of similar, but for different reasons, which is why i explained it so you hopefully understand the differences better. it wont purposely limit my power but does go down.
aaron