It'd be interesting to compare the scale at which these providers operate and see if the deploy time grew over time as the company grew.
I am wondering if Reflame would be able to achieve the same results if it had even quarter of customer base as Cloudflare or Netlify or Vercel.
The biggest limitation, and apples-to-oranges of this comparison is that it seems to me - from what I gather from the homepage - that Reflow only allows to deploy React. The bigger players listed allow all sorts of frameworks and runtimes to be deployed to their edge. I am guessing that optimizing for a one very specific configuration - React is way easier than to support many different flavors and build systems.
Lastly:
Every service tested here, except Reflame, currently uses the term "instant" to describe their preview deploys:
This is a little disingenious since you did write "Reflame deploys client-rendered React web apps instantly" in your Show HN [1] so maybe don't be hypocritical.