We did the PACT study with DS1, but were in the non-treatment group. It turned out that with DS2, a clingbot, to care for, I wouldn't have been able to travel to and participate in all the "intervention" sessions with a bouncy DS1. It's 4 or 5 years ago, so I can't remember the details of how frequent they were meant to be - it was weekly-monthly rather than daily, as ABA interventions would be.
Having seen the video presentation of the interventions involved when the results were presented, it was encouraging a really intensive sort of engagement with the child with ASD - more than would come naturally to most people and given the number of people I know who unfortunately struggle to interact in a positive way with their NT children, I could see where it would be of benefit.
The sample would have been far wider than that, though. The ADOS style assessments were carried out several times over about a year and in that time, DS1 went from refusing to engage with the tests unless I administered them and showing as significantly language delayed to reading the script over the assessor's shoulder and telling her all the answers straight off and coming out as age appropriate in the language assessments.
In the end, they concluded that the effect of the intervention wasn't significantly better than that of sending parents on an early bird course. There's so little research like this that it sounds like a luxury to suggest it, but I do think that research should cover the effects of interventions on targeted groups and not just in a blanket manner.
The PACT study also focused on higher functioning, verbal children with ASD, so there are still no studies like this on the effect of interventions on non-verbal children. One thing we've found over the years is, that while there have been various sources of help for DS1, there's been very little for DS2. He was abandoned by OT because he couldn't complete the tasks they set for him. Yes, of course he won't even touch spaghetti, that's why he's with your service! The school paid for some movement disorder advice for him, recently. They tried to get him to walk along a winding skipping rope and he wouldn't, so they declared that they couldn't help him.
I'm veering off course, anyhow. I don't see the proposal for this study as being all about the "refrigerator mother" theory and don't find it offensive in that sense. I do think it's trying to get at the idea of early intervention and explore how useful pro-active intervention before there is a diagnosis one way or another could be. But yes, it's very clumsy about it. From a personal point of view, DS1's diagnosis made us more alert with DS2 and we were looking for things that needed "work" before we even asked for an evaluation for him.