There’s no general preference Satya. Left to right was prioritised in the first video because most people know how to add from the right. You are right of course that it is easier to start with the units because we are accustomed to that, but most people do find that left to right is often better once you get used to it.
In Vedic maths we say to use the method you prefer. Most people prefer the most efficient method. But you won’t know the most efficient method unless you have had a chance to compare them. So as teachers we need to be fully familiar with all the possibilities and fluent with them. And we don’t say a method is wrong because we prefer a different one. All methods are valid.