That is irrelevant as I have explained. What it does is reduce the network effects (merchants accepting and holding Bitcoin thus being nodes in the Metcalf law valuation) within the Bitcoin ecosystem that those holding fiat must buy BTC to attain. If everything they can buy with BTC they can also buy with fiat, then there is no great need to buy BTC with their fiat.
That was precisely my point about why lose 3-5% on double exchange, when one can just buy with their credit card for 0%.
Many people prefer to use BTC rather than credit cards, even though they can use either, because BTC is faster and more convenient for online payments. They buy, wait for the price to increase, then spend when needed. It's that simple. I do not think this 3-5% double exchange loss you are talking is a significant factor in whether or not people choose to use or accept Bitcoin.