PIP MR review descision

A few months ago I underwent a PIP home assessment.
The result was that I had my mobility component reduced from 12 points high rate to 10 points standard rate.
I enlisted the assistance of my MP and I requested a MR.
This resulted in the DWP upholding the decision to reduce my award.
I took a massive gamble and I applied for a tribunal oral hearing.
To cut a long story short the DWP emailed my MP stating that they would not be attending the tribunal oral hearing and that my case was being looked at by their complaints department.
I received the bundle from the tribunal service and I sent them some important medical documents, a supporting letter from my GP and a carers supporting letter, all of which the DWP had failed to forward to the tribunal.
About six weeks later the DWP rang my home number.
I was in bed ill and my carer took the call and explained that I was too unwell to take the call.
However the man who called absolutely insisted on speaking to me even though my carer explained that I had previously told them not to ring me but to communicate in writing and to liaise with my MP.
I was so shocked and taken aback that I then reluctantly took the call.
The man said that he had looked at my MR request and the outcome and that he had decided to reinstate my higher rate mobility.
I had asked the tribunal service to consider 4 points I thought I should be entitled to for planning and following a journey and the evidence I had supplied to the DWP had been completely dismissed by themselves and the assessor.
I also asked the tribunal service to consider a longer award due to my health conditions being chronic and having worsened over time and that repeated assessments had a negative effect on my mental health.
The DWP man said he was able to extend my award from the three years granted to five years.
I was hoping for an ongoing award and if I had attended a tribunal I would have requested that.
I was so shaken up with anxiety that I agreed to what he was offering me even though I regret agreeing to the length of the award.
When I received the decision letter I was amazed to see that I have gone from previously been given 0 points for planning and following a journey because "the threshold is very high" to now being awarded the full 10 points.
How on earth could the assessor and the DWP have got this so wrong and caused me so much unnecessary upset and distress.