It depends on how much Indica is paying extra, it comes to a crossroad where it exceeds the cheaper rate of a fixed loan because it reduces the time period of the loan and cuts back on the principal amount that the interest applies to.
Not really. Definitely giving money away for free.
At its most basic, (i know you know this) if you're paying interest on a loan, the faster you pay off the loan, the less interest you pay over time. So in a traditional sense by making extra extra repayments, you indeed are are paying it off faster. BUT there's
ALWAYS ways to pay even less.
There isn't a really a vector on a long term mortgage where this crosses over and renders the strategy useless unless Indica was going to pay out their mortgage in less years than the mortgage was fixed for. To put that into perspective, that extra repayment would be to the tune of +~14k per month on a 500k loan). At which point the strategy has no weight. However in all other scenarios, you save in interest regardless of what extra you want to pay.
Look at it this way If you wanted to pay off a 30 year mortgage in 15 years, You could still have taken a fixed interest period and pay the loan off within 15 years. You're just deferring when you reduce your balance to three years in (or however long you took the fixed period for).
As i said though that ship has sailed, CBA fixed rates currently sitting at 1 year for 4.99%, 3 years is 6.39% and 5 years is 6.69%.