The problem isn't his cite it is his math or maybe his understanding of the words in the Code.
When you write this you are wrong: 50,000- (49,000-49,000)=50,000
The amount of current outstanding loan the moment before the new loan (and moment is a better word to understand what the IRS is means when the say day) is $0
So the math goes like this: 50,000-(49,000-0)=1,000.
Look at the IRS example in the link provided by Mike P.
If you don't like how the IRS is using the words " the outstanding balance of loans from the plan on the date on which such loan was made, " take them to court and good luck.
But what they have consistently said in examples, regulations and so forth is the balance the moment before the new loan is issued is what those words mean. .