I don't think that device exists, its hard to say something like that.
But I can tell you for sure that this kind of device wouldn't be very efficient or useful, let's assume you are using water for cooking, if you want to boil it and cook your food at higher temperatures you would use higher pressure, for lower temperature, lower pressure, but there is no need to control it with precision since the boiling temperature shows little variation with the pressure (at 2 atm you boil water around 120ºC, at 0,5 atm it is around 80ºC), so you basically have a pot that can be ajusted for high pressure or low pressure cooking, but without precision.
A second factor to consider is the packing, to go higher than 2 atm (where a normal pressured pot gets) you would have to get a more expensive packing system to prevent your pot from exploding, so now we have a regular pressured pot with the option for low pressure.
The low pressure system wold be quite complicated to develop, since when you boil the water it turns into vapor and will raise the pressure of your pot, so you need something that will keep put vapor out of your system, something like a pump would have to be constantly working fot that to happen, that's not very practical.
And at last, I can understand why you would want to cook with higher pressure, I do it quite often myself, but I can't see a good reason to do it with low pressure, there are many cooking techniques that use vacuum, sous-vide for exemple, but I have never seen one that uses it in a sealed pot like you are proposing. You could say you want to cook in low temperatures which is completely fine, but you can do it in a less complicated way, like using an electrical heater and thermostat.
So it may exis, but as i said it would be unpractical
For the most part, the buttons just have pre-set cooking times. For other times, then it's best to just use manual modes. A few of the programs are particular, like the bean, multi-grain and porridge programs have a long pre-soak before pressure cooking. And newer models (SMART, DUO-ENW) have the rice program pre-set to cook at "low" pressure.
Instant Pot made nice little charts of these programs and posted them online.
In my personal experience, the extra soaking time of these programs just takes longer - especially if you're already using pre-soaked beans.
That's why I always use manual mode - and the recipes I wrote for their recipe booklet always call for it as well.
Best Answer
It is going to depend greatly on what you cook and where you are. Long braises can be shortened by hours. It is nearly impossible to cook beans in Bogota Colombia without a pressure cooker. cite
Lentils on the other hand. The recommended times in the IP manual and on the bag for not in a pressure cooking are the same. And as you say, with the IP natural release is not included in the time given.
Another time savings is not having to manage the cooking in the middle. Thanksgiving evening dumped turkey carcass, mirepoix and water. Set for 2 hours of high pressure. Ignore for three hours. Cool and refrigerate one gallon of turkey stock. No checking to see if it is simmering, adjusting the heat up, checking again, adjusting the heat down.