I don't believe this to be true. I'd be very surprised if it was to the extent its being reported. I'd be interested to hear findings more about it if its looked into.
"DNR notices" don't exist anymore in the UK. There used to be a red-bordered form denoting that but they've been replaced by advanced care plan (ACP) with a separate purple RESPECT form (Recommended Summary Plan for Emergency Care and Treatment) which codifies patient's wishes with regards to preferred place of care and ceiling of therapeutic intervention.
In the event patient were to lack capacity then discussion is had with family members. If somebody has lasting power of attorney for health reasons, their wish takes priority, otherwise its a designated next of kin whose input is sought out.
And that form has as a mandatory part filled in with regards to documenting what was discussed with family, where and when. And it is countersigned by a senior doctor (either registered GP or hospital consultant) with registration numbers.
Also to note that CPR is brutal. In elderly patients or those with co-morbidities, it is an undignified and cruel thing to do. The decision to do that or not do that, and also to offer ventilator or escalate to ITU is legally up to the medical team to decide. But we do take patients and families wishes on board as much as possible. Also DNACPR doesn't affect treatment or escalation of care. CPR also has a very poor survival in the context of a disease like COVID, it’s value is greatest following a heart attack, usually in a young-ish patient, but chances of surviving post-return of spontaneous circulation even in hospital setting is very low, something like 10%. And there is usually a lot of damage done due to hypoxic brain injury etc.
Learning disability in of itself in NOT a reason to say somebody shouldn't be resuscitated. Learning disability patients have hospital passports and care plans on how to ensure their hospital stay is as minimally traumatic as possible and so that they are holistically looked after in hospital and community. Separate from DNACPRs.
I've done DNACPR discussions with patients with learning disabilities but those who are really frail, elderly or with complex medical conditions and these consultations take hours, with feedback from patient, carers and families. It is an important discussion, reporting around it and understanding about importance aspects of it is pretty woeful in the UK.
There's more here
https://www.bmj.com/content/371/bmj.m4069
Sorry for sidetracking the thread, it is something pretty close to my heart for more than a few reasons.