The start of day, full charge ev range estimate is created by multiplying a computer calculated estimate of the vehicle’s average ev mileage (based on historical driving data collected by the computer, weighted for more recent data) by the amount of usable available power.
Keep in mind that no matter how far your drove the previous day, the full charge ev range estimate for the Gen 2 will be determined by multiplying a usable power amount of ~14.1 kWh by an ev mileage number. The question is, how does the computer algorithm calculate that mileage number? Is there a fixed limit to the displayed range estimate (as 50 miles was for the 2011/2012 Volts and 60 miles for the 2013/2015 Volts), or is your displayed 86 mile estimated range accurately reflecting recent achieved "ev mileage?"
The kWh Used number shown on the energy usage display screen is a net calculation (grid power used less regen put back into the battery). Nissan Leaf owners once had a "Carwings" app (perhaps they still do), detailing the power consumed for each trip as a sum of the battery kWh Used (positive) and the regeneration obtained during the trip (negative). It could be the Volt computer maintains the same grid power/regen power consumption data, and uses total trip power consumption data, not just grid power data, when creating the "average ev mileage" number used to calculate the full charge range estimate. How much regen power was included in the total power you used to drive those 90+ ev mile trips?
Your route apparently included a lot of downhill driving. Driving a route that allows you to add a significant amount of downhill regen to your "Electric Mode" fuel supply might allow you to drive more Electric Miles, but if the "level terrain ev mileage" you get from use of grid power is about the same as the "level terrain ev mileage" you get from use of regen created power, the start of day, full charge 86 mile ev range estimate might well be a calculated number, not a maximum number. The full charge range estimate isn't going to estimate how much regen and regen miles you might get that day.
Your ~500 ev miles in a day post mentioned that you added some Electric Miles at the end of the drive by using Mountain Mode to recharge. It could also be that any "Electric" miles driven on MM recharged battery power are excluded from the start of day algorithm’s average ev mileage calculations. My 2012 Volt has the quirk that allows MM power to be counted as Electric Miles, but the kWh Used number on the display does not change as the power is used. This quirk once produced a display screen showing I had driven 89 Electric Miles on 9.8 kWh Used. The following day’s full charge ev range estimate did not receive a "bump" from this "I averaged 9+ miles/kWh over ~90 miles" achievement. By not increasing the kWh Used number when MM-recharged power is used, the computer is identifying it as "not grid power," so perhaps the computer also does not include any "Electric" miles driven using the MM-recharged power when calculating the average ev mileage to apply to the full charge ev range estimate calculation.
Perhaps these observations will add to the discussion of how the ev range might be calculated.
I note that neither of the two charts you posted indicate a full charge electric range for a 2017 Volt of more than 70+ miles, suggesting the 90+ mile numbers you are getting are much rarer. Our friend Ari C drove 114.0 electric miles on 14.4 kWh of power using his wife’s Gen 2 Volt (no gas used, no gas miles), so it is indeed possible to reach those distances on a full battery charge. If I recall correctly, his next day full charge estimate was 84 miles.
Your description of the route you used for your ~500 mile in a day drive seemed limited to level terrain, downhill, level terrain, downhill, ending with a little Mountain Mode recharging. The finer details of the achievement, such as average speed and how the other drivers on those roads were reacting to such slow driving (and where those roads are, for others who might like to attempt to reproduce your results), were not given. The implication is also that your long electric drives are achieved because they include several downhill sections (for regen), and are not round trip events. Ari’s 114.0 mile drive was mostly driving in a big oval on relatively level terrain. It doesn’t seem unreasonable to expect someone who posts pictures of a usage screen showing 186.8 and 199.7 electric miles driven using only 14.2 and 14.1 kWh with no gas used to elaborate on how this was achieved.