Charts can be helpful for general guidelines, but they are not to be taken as gospel.
I've had AGM batteries that rest truly fully charged days off the charger, at 13.16v, 0.4v above that chart @65f, making that chart on those specific batteries almost completely irrelevant..
Voltage alone is always misleading. It is not a fuel level gauge as so many seem to think.
How many volts can the battery maintain under X amount of load, at what battery temperature?
How does this compare to other temperatures?
How does this compare to when the battery was newer?
How does this compare when the battery has seen a plug in charging source applied overnight or longer?
How does this compare when blasting the stereo with the engine off for 10 minutes?
Its just a battery, they are rented, does it really matter? replace as needed.
A voltmeter with voltage sense leads directly on the battery terminals, every time the engine is started, will give the user much more information as to battery state of health, and state of charge, and give ample warning when a no start is becoming imminent. Such a voltmeter also unravels the mystery of the vehicle's voltage regulation, which nowadays can intentionally sacrifice the battery for tiny gains in mpg's.
Likewise when charging, knowing how many amps the battery is accepting at what voltage is paramount to understanding when the battery is indeed fully charged. 95% charged is good but only half as good as 100% in terms of keeping the battery happiest for the longest span possible. A battery charged only 30%, can still likely start your vehicle. Funny how many people think the battery which can start the engine is healthy and therefore fully charged.
Every battery Starting/deep cycle/ marine dual purpose maintainence free flooded or AGM I have taken off a 'smart' charger whose green light is on, has accepted more Amphours/watt hours from my adjustable voltage power supply set at 14.4 to 14.7v as amps taper further. Often it takes 3+ more hours at 14.4v before it can be considered fully charged via amperage or with a flooded battery, when the hydrometer's specific gravity reading stops rising . I usually get 10 to 15 more Ah into group 27 or larger batteries rated at 100Ah capacity and it takes hours and hours. Very rarely does my Adjustale voltage power supply's ammeter and voltmeter acree with teh smart charger, and when it does it is on a newish battery that was unintentionally discharged. Every time I charge an older battery the Adjustable voltaeg power supply is aboe to return 5%+ more into the battery
The Hydrometer does not lie. A voltmeter can. The green charger light does.
The older the battery the longer it takes to achieve full charge, and the more it needs that true full charge in order for capacity decline/performance decline, to not accelerate.
The deeper the discharge, the more important the proper recharge becomes, and it takes much longer than people expect, and may products, despite their marketing and owner/fanboys, are incapable of achieving a proper full recharge.
Good enough, is subjective....opinion, not fact.
If one does intend to achieve full charge of a lead acid battery, they need a charging source capable of maintaining 14.4v+ for as long as is required either for amperage to decline to a certain level, or for the hydrometer to indicate specific gravity of the electrolyte is no longer rising, and preferably both methods if possible
Full charge via amperage acceptance cannot be determined at lesser voltages, so a 'smart' charging source which keeps reverting to float prematurely is not doing the aged battery any favors, and none of them have hydrometer probes. So 'full charge' is a best guess algorithm for as wide a spectrum of starter batteries as possible. One size fits none, but any charging source applied to an undercharged battery is better than none.