The requirements for TN are laid out clearly. If you show up with a degree not matching job requirements or an inadequate TN letter then it's a guaranteed rejection. Some just show up with just an offer letter thinking it's a right of passage and are promptly sent back.I agree the statistics is 90% or so of success, I should have been more specific what I mentioned earlier was hearsay from the colleagues and friends who were trying TN visa, they from GTA usually try at the Niagara borders. Those Asian folks who got repeatedly rejected said half of the applicants who attended with them succeed and other half fail. The failed ones often get blacklisted and keep failing forever so give up after 3-4 tries.
My personal experience during a business travel from Hamilton, ON to NY I was once stopped for secondary screening. The reason is I had left USA in 2008 at the peak of GCC, then I had been fired from my job with JP Morgan and was not able to find a new home. During this 2022 business visit now, I learnt I had been flagged as missing migrant possibly who became an illegal in 2008. Thankfully I carried old passports had paper i94 copies etc...But still I could see disdain in the eyes of the officer who questioned me. I waited for 3 hours. That border office is quite open and I could see many TN visa applicants, I felt 75% of approximately 30 applicants I saw that day were rejected, one officer was simply rejecting everyone who was going to him for interview, I saw 3-4 folks walk away with tears. Which is why I quoted race in one of my posts. Also weirdly some of the applicants could hardly speak English and I was wondering how did they manage CLB 6 in English, they are not Francophones either.
I drafted the letter myself and had the CTO sign it.