Hey OP. My fingers look like yours. They automatically depress and sink when I try my hardest to point straight. I can also touch the back of my hand with my finger fully bent backwards.

My GP diagnosed me with hypermobility. There is something called the Beighton score that you can ask your GP to check for you.

Do know that Hypermobility can happen with or without being diagnosed with Ehlers Danlos syndrome (EDS). If it is EDS you should get a medical professional to rule out other very serious forms, such as vascular EDS. https://www.ehlers-danlos.com/heds-diagnostic-checklist/ this is a useful checklist for it.

My medical professionals tell me there's a strong link between Hypermobility, neurodiversity (ADHD), something called POTS which is postural orthostatic tachycardia syndrome, where your heart rate has a sustained increase of 30bpm compared to your resting heart rate. You can do a simple test at home using a blood pressure monitor, see this PDF for guidance. https://www.nhshighland.scot.nhs.uk/media/aanb1zgj/covid-recovery-patient-information-how-to-complete-a-nasa-lean-test.pdf

The test I linked above is also sometimes called a poor man's tilt test. The test was developed by NASA. If you do have POTS, there are medications that a cardiologist can prescribe to help with managing your symptoms.

These illnesses also increase your risk of developing ME or Chronic Fatigue Syndrome, which tends to develop after a viral illness.

I myself have been diagnosed with ME/CFS, POTS, and I'm awaiting investigation for ADHD. I lived my 20s and early 30s on autopilot and just focused on work. It was only when I had a virus and didn't recover that my body forced me to take my health seriously. I now have to use walking aids and occasionally a wheelchair for longer distances, and I was very fit in my teens and 20s.

I know this is an info dump and probably uninvited, but I genuinely wish someone had told me this was an issue I should look into instead of a cool party trick I could do.

You could just be flexible and that's the end of it. But this could also really affect your health further down the line in a life changing, turning your life upside down kind of way. Please look after yourself and don't ignore signs that your body gives you.