Whilst flight is in either simulated IMC or real IMc, I know of very few instructors who will actually instruct if the cloudbase isn't 1500ft at least for an IMC rating.
I tend to agree with this also. Whilst I did my intense course in just 5 days inlcuding the exam, there was 1 day where the cloud was a solid 900ft, tops of 2300ft. I queried why we wouldn't train in this as I was likely to take off in said conditions. It was down to instructor opinion that should the engine fail and you are in IMC / on top and have to descend through a solid layer of cloud to only 900ft, you have perhaps less than 60 secs to select a suitable landing place. You may end up on the top of a congested city, perhaps terrain depending if you had a full instrument failure / disorientation.
If it was broken / scattered 900ft, so you could see something below he was quite happy.
Just worth pointing out that whilst we, who may fly in said conditions, the OP FTO may have their own limits which may hinder training.