I don't think the level of proof you're looking for exists. There weren't any lawsuits because nobody started companies because they knew they'd be sued out of existence. I can tell you that Stratasys was aware of and leaning on the (open-source, non-commercialized) RepRap project at the time:
https://reprap.org/forum/read.php?1,13528
and that they're more than willing to sue small companies, even after their main patents expired:
https://3dprintingindustry.com/news/stratasys-lands-blow-in-...
They eventually settled that suit because the patents involved were a bit weak, but I doubt they would've settled if the earlier ones were still in force.
I don't know where you saw that RepRap was commercialized in 2006 but as far as I know that's not true. Here's a history of the project by its creators which puts the first RepRap-based company in 2009: https://all3dp.com/history-of-the-reprap-project/
You could probably buy pieces on forums before that but Stratasys wouldn't target individual forum posters with runs in the single digits.
Makerbot, Prusa, Creality, FormLabs, and the other big names in small-scale 3d printing are all post-2009 companies. Here are some more recent examples of patents blocking 3d printing: https://techcrunch.com/2016/05/15/how-expiring-patents-are-u...
The SLA (liquid) section is the most relevant; it mentions how FormLabs lost a lawsuit for building one early. Other companies didn't attempt to beat the patent, but Prusa, Creality, and Makerbot (ironically now owned by Stratasys) all began selling SLA printers shortly after the patent expired. I don't have statements from the executives that they waited because of patent issues, but barring that the situation seems clear.