I saw a video one time where a guy took all the slides from a global warming presentation and then looked at the source data. Every slide had a different starting time period. He proved that the timeline on every slide started at the most advantageous time to prove the presenters point, but when you looked back there were just obvious cycles and overall the slides meant nothing.
Yes, I know the one you are talking about.
That might well have been Lord Christopher Monckton (though I could be mistaken) who used the chart of temperature measurements over time and used a moving average coupled with a straight trendline and then displayed that trend line (which smooths the data) in various time frames.
Coincidentally-or not conincidentally-he was able to show that while the trendlines they showed to support their assertions of increasing global temperatures that were caused by man, he was able to show just as many or many more that showed declines in temperature over time.
As you sagely pointed out, they were trying to be clever by half in their selective choice of where they wanted their trendline data set to begin.
They likely thought they were so clever that nobody would notice.

I think what you're saying is kinda the same thing.
The industrial revolution was used in many studies...because it concluded "Man did it"...