Who is right here?

[Howcanwehelp]

Dh and I have different approaches to our children's homework. They are year 7.
I make time for them todo it, make sure they have access to equipment and answer any questions.
Dh is literally doing the homework for ds, talking him through each point. He obviously doesn't get it and I think leave it and explain to the teacher he doesn't get it. It's been going on for hours with lots of shouting and stress on both sides. Ds has additional needs and the teacher needs to know he can't do the homework.
So my method, let him try to do it, get it wrong and let the teacher know he doesn't understand it and is too lazy to do it properly. Half the argument is about him guessing instead of measuring.
Dh method, keep explaining and arguing with him for hours until its done.
I know dh method means the homework gets done better but I really hate the arguing and fighting to get it done. Ds would rather have an argument then try to do it.
I think I under estimate what ds can do and dh over estimates him.

I think your DH's method is extremely damaging and will damage both your DSs relationship with his father and with learning. It will turn him off homework altogether and will also damage his self esteem.
Personally, I don't think either of you need to be this involved in DSs homework. He is at high school now and his homework is set to be completed independently. At most I would check homework had been completed, but absolutely not be involved to this level.
As you have said, it is not DSs work when your husband has got involved and does not show the teacher what he has and hasn't understood which the teacher would then use to plan learning in future lessons.

The homework is technical drawing and ds just doesn't get the fact it needs to be a scale drawing, so not life changing or essential. I think I allow him to give up too much but I hate seeing him struggle.

Well, insist he tries his best, applies himself, but still don't force it. Your husband's method is still damaging- and as you said, doesn't actually result in him understanding it any better.