Not charging fully and not depleting fully, resulting in about perhaps 13-16 EV miles per drive, so that in four years you'll have 16-20 EV miles per drive on a full charge is completely ridiculous. Why would anyone not want to get their full 18-21 miles per charge right from the get-go? That's gotta be the dumbest argument I've ever heard. You're basically advocating that people drive their car like the battery capacity has already diminished so that some day in the future they can drive the car on a full charge and use the full capacity to go even farther? Duh! If the battery is doomed to degrade, then what sane person wouldn't take full advantage of the full range before it does?! If this car's battery is so bad, then how is Ford tricking y'all into buying their Energi cars? lol. Anyone who buys a Ford Fusion Energi only to worry constantly about battery degradation has bought the wrong car.
There are indications that Ford didn't design this battery well enough for battery longevity.
1. It's a small battery, see C rate explanation above, and there are also DoD (depth of discharge) concerns (e.g., Ford's removal of EV+ on 2018s) and concerns over more cycles.
2. It has no battery heater other than cabin heating. Even the degradation-prone Nissan Leaf has a battery heater. Why would the other manufacturers incur the expense of a battery heater if it wasn't needed for EV-mode use?
3. It is only air cooled, most larger battery EVs have superior liquid cooling and heating. Why wouldn't the other manufacturers use cheaper cabin cooling? Especially if it worked adequately in such a small battery.
4. There are numerous reports of early Energi HVB degradation, which seems to validate concerns 1-3.
We're owners now, and have to choose how to deal with the perceived design weaknesses, just like we need to deal with the apparent 12V battery design weakness (install AGM? carry a charger? trickle charge often? Triple-A membership?) or any vehicle's weaknesses or pattern failures.
If one wants to eek out every last EV mile in a carefree manner, then that's one position (yours, apparently). Downside is that if you keep the car for a long time, its EV performance will likely be diminished if your usage patterns stray into bad practices too often (e.g., high SoC and high temps, frequent full DoD, multiple charges/day), maybe at as early as 30K or 50K miles (or 20K for the Florida couple who kept it plugged in all the time to a L2 charger). Downside is likely minimal if ownership is expected to be short lived (e.g., trade in car after a few years), except for sticking someone else with a degraded car.
On the other hand, if one wants to maintain their Energi at near its peak performance over the long term, then that's another position. Downsides are it requires learning, and attention to charging/discharging details, which can be tedious for some while not very bothersome for others (I like Consumer Reports' summary that it's a car for gadget lovers), and that attention to charging/discharging details will sometimes have you refraining from using as much EV as you would otherwise like, in conditions that will be harmful to the battery. It's possible that some may be be lucky enough that their personal driving patterns allow for almost constant EV use while also adhering to best practices (e.g., a 12 mile commute and charge-discharge of 80% to 20%).
At 100K or 120K miles, depending on driving patterns, it's conceivable that the two different types of use could result in the same number of EV miles (maintainers will be able to drive more EV miles later in the car's life, just because there are more available).
Both are valid positions for different subsets of people.
P.S. "the battery is doomed to degrade" is not true, at least not at the same rate of degradation. Articles and models and expert quotes I've seen indicate that adhering to best practices might very well maintain this battery just fine over the long term.