Regarding Lotus Lab, as Bron said, Richard, Wimon and Billie Hughes wrote THE books on corundum. I consider their lab one of the best out there for Sapphires, Rubies, and Spinels, particularly when it comes to their color grading. They're one of the few labs that won't call EVERY piece of pink corundum with a smidgen of orange and/or brown modifier "Padparadscha" (looking at you GRS and GIA).
I bought an unheated yellow sapphire from ClassicCeylon a few years ago. Seenu is a trustworthy man and his pictures and videos accurately represent what the stone looks like IRL (at least, this was my experience). I believe his family operates a few mines in Sri Lanka.
From the photos and video, the first 2.17ct you posted looks like a nice prototypical example of a Sri Lankan cornflower blue. I think it would be as beautiful cornflower blue that would likely hold its color in as variety of lighting situations, but it's unlikely that it would be "glowy" like the best of Burmese cornflowers. Then again, it's a fraction of the cost of a Burmese cornflower. Depends on what you're looking for and what you're willing to pay.