Do we really know that? I don't think so.
Also, it's interesting to consider that a SoC using SEC 8nm will have more than double the die area. And TSMC has better yields too. These two make a huge difference in the economics in play.
The prices for Samsung's 8nm was almost half the price of an N7 TSMC wafer. Which cost 10k in 2020.
This is the reason went with Samsung, despite it's process node being a bit inferior to TSMC's N7.
Today, N5 costs around 17k per wafer. So even with the chip size reduction, the cost per chip will be lower on Samsung's 8nm.