Halving does not reduce the supply nor does it make bitcoin more scarce, the total supply of bitcoin will always be 21 million BTC.
You are correct but I think what he meant is that bitcoin mining supply is reducing through halving.
This is indeed a unique feature and was the catalyst for the previous bulls but we don't need to exaggerate. Because so far, more than 19.5 million bitcoins have been mined and there are only 1.4 million bitcoins left to be mined. In addition, there are many other factors that make bitcoin unique and help increase its value.
I only see two things that makes bitcoin unique. They are limited supply and being the first cryptocurrency. So these has helped it to make people prefer it. Other coins are coming but people will focus more on one while less focus on the other just like how the world focus more on gold while not really focus on others. I hope you will understand the less focus that I mean.