PIP ‘I’ or ‘he/she’ when completing for another

Hello
The PIP form states to only write ‘he or she’ if you are writing on behalf of someone else if you are their appointee. But to write ‘I’ if you are writing on behalf of someone else when they are providing the information. I’m writing the form for my son because it’s too overwhelming for him but he has capacity and has provided the information.

However, I have seen advice on here to write ‘he/she’ if you’re writing on behalf of someone else because they’re overwhelmed, because writing ‘I’ (even if you explain somewhere on the form), makes it look as though they’ve done it themselves and are therefore completely capable.

Please advise??
Many thanks

Thanks Chris that is helpful, but just to clarify- my son is giving me the information (past and present), but he is not sitting with me when I type it. So - it’s definitely his information, but it’s my wording. What do you think? And he will read and sign all.

Hi Alpro cherry, for what it's worth, I've just done someone else's review form for them, long distance. I got them to sign the two places at the front and the consent to contact doctors, and post me the form. I have filled in the rest.
For all the activity questions I have typed [dictation software!] the questions and the claimant's answers. I've just written
"See Doc No. X" in the stupidly tiny boxes now provided.
And throughout I have said " Miss Smith cannot..." "Miss Smith whatever" using the claimant's name. I filled in my details in the section at the front provided for this. Because of the distance it wouldn't have been practical in this case to have the claimant sign each page.