GP/Consultant wording for PIP

I was wondering if someone could clarify my understanding of how GP's and consultants word things, or more importantly how the DWP interpret the wording, for example a GP report may say 'he suffers with bilateral knee pain, he says he is unable to walk more than 3-4 steps due to pain'. The knee pain is a fact because they have xrays etc to confirm that. He says is more confusing to me, do they word it like that because they have no proof, physical palpable proof of pain, and have to word it like that for legal reasons or is there another reason for wording it in such a way.
Any insight would be greatly appreciated.

Hi get them to write how your disabilities functioning wise as well as diagnosis if you can.

The medical evidence sent on paper has to be “robust” to enable the test for benefit to be met, and should include comments about how functioning is affected.

My GP always used those words, XX says that ...... but he finished off by saying he had absolutely no reason to doubt me.

I think GP's don't always realise the impact that their words could have, when we told the GP what the DWP had previously said about mobility he said 'that's ridiculous I am going to put that you can't walk for more than 3-4 paces'. But now the DWP have decided to use that against my husband because they say in his assessment he said he could walk for 2-3 mins. What he actually said was that it would take him 2-3 mins to walk the length of our garden, 25ft, before having to stop because of pain and couldn't do it again for about 25 mins. So they have definitely chosen specific wording so that can put a completely different skew on things.
It would be more helpful if GP's etc could write 'he tells me he can only walk for 3-4 steps and this is consistent with his diagnosis of........' of course the DWP could completely ignore this too, as they seem to have been doing with any relevant evidence that claimants send in, but it might just help clarify the point to the DWP.