Quite.
My friend's son was initially refused DLA, despite diagnoses of autism, PTSD and generalised anxiety disorder, but I helped her get the decision overturned at a mandatory reconsideration.
PIP's the same. I recently retired after spending several years working in welfare rights, and every PIP appeal I've ever done was successful, because DWP decision making is pisspoor and the system is stacked against the claimant. My DB was on the standard rate of PIP for daily living; I helped him with his renewal and he's got enhanced rate of daily living plus standard mobility, which is exactly what he should have been getting for the last 4 years.
Imo, the DWP treat it as a numbers game, they turn down valid claims or make awards lower than they should be because they know that a lot of people simply won't have the energy or ability to challenge their decisions.