Please let me know where to refer in TD documentaion to get better understading of this.
I was trying to find some good source of information to check this syntax, finally I found the below document which describes that this syntax can only be used with inner joins, See the line
"converts ANSI‑style inner join syntax to comma‑style syntax if the entire query is based on inner joins"
In the SQL DML manual there's a lot about placing Outer Join conditions in ON vs. WHERE.
This also includes a rewrite of an old article from the Teradata Review magazine as a case study. I remember the original title: "A lesson on outer joins learned the hard way" :-)