How does Pretext work?
- Segment the text; Normalize whitespace, apply Unicode line-break rules, and split the string into measurable units using the browser's own text segmentation.
- Measure with Canvas; Feed each segment through Canvas measureText() to get real glyph advance widths from the font engine. Results are cached.
- Pretext.js uses pure arithmetic; Given a container width, compute line breaks by summing segment widths. Multiply line count by line-height. Return height. No DOM, ever.
Unfortunately, that doesn't really explain the final integration. And it seems I misunderstood/-assumed at first.
Looking at the example at the top right, it renders numerous div elements?
So, presumably, you lose text wrap behavior and clean markup like <p> for a paragraph? I also can't select text from it in a normal or consistent way.
This example isn't very convincing either.

Seems like a cool visual gimmick more than practically useful and accessible for primary content.

So, assuming good faith, they used two Telegram bots for some service functionality
Obviously, that should never happen silently. But these findings don't necessarily mean data has been compromised [beyond the scope of the app itself].
I get they may be very frustrated and annoyed at the negative blowback after their FOSS efforts, but dismissing concerns isn't a good way to respond.