I do understand your cynicism as I have enough bad experiences with the English motor trade to have a mountain of it but do have to give credit where it's deserved. OK yes it might be just upselling but if it is needed then it is, if is not of course that is another matter and if they want to sell it or actually offer a service then yes they need to give more information as an explanation of the benefit or need.
In this case you put that they asked if you have a battery charger so it's not an out and out up sell, if they are finally advising customers about the need for battery recharging on these modern cars it is a good thing because as I put before many older drivers have forgot about this simple easy, clean hands car maintenance that can save a lot of time, hassle and money from car problems and breakdowns.
It may also be the case that older drivers don't realise the greater need with the more modern cars but they should know really, where does the energy come from for all the driver comforts, "aids" and "assists", Just think of a list of all the electric items on a modern car, just with the buttons you can press to use them let alone all the ones the car itself uses.
Let me assure you that from a previous life and experience generally I know that not all customers are great and many just want the bare minimum done to the vehicle often they don't really even the bare minimum but are forced into for some reason and even then they may ignore things like safety and statutory requirements and it's not a matter of they can't financially afford it.
Obviously I have no idea of the state of charge of your battery and the Dealership could have been trying it on (again) but it is possible that the battery might need recharging it depends on many varying factors, or it might not desperately need recharging but might be best recharged. To force the undersized boot on to the other foot you did not have the figures for state of charge to know anyway, which is bad on their part. Also state of charge is not the full story about the battery but an indicator.
There are many threads and posts on Briskoda for the various models of the issues that a battery in low state of charge has caused with the poster often unaware that the low state of charge is the cause of these unexpected warning lights, messages, error codes and issue(s). Of course not all issues are caused by low state of charge but many more than the average driver realises, the car 12v battery is very important and always has been but especially now on a more recent modern car.
That may or may not be the case with your car, I can't know, or it could be a con I would never rule this out, but certainly there are many cars where it could well be the case that the battery needs recharging, to be more dishonest they would try to sell a new battery.
I've not seen battery replacement mentioned at 2 years but I have 3, even VW put 4 years but there is no reason why those batteries could not have lasted a lot longer by the use of recharging, best done as a preventative measure than a distress need.
Some people prefer to just use, abuse and neglect the 12v battery and replace it which is fine and their choice, to me that seems wasteful and expensive but it keeps the economy going round.
So have you checked your battery to see if it does need recharging, that of course would be now rather than when at the Dealership.