I’m not sure there is a right or wrong, especially if the thing to maximize on would be “fairness”.
As you could argue everyone paying the same nominal fee for a swap would be fair. But you could also argue that everyone paying the same percentage fee would be fair as well.
A tiered system is somewhere in between those extremes.
Generally, it’s quite common for exchange fees to be tiered, e.g. see the coinbase CEX fee tiering: https://help.coinbase.com/en/exchange/trading-and-funding/exchange-fees
I think it’s fair to question on the impact on total fees. Intuitively it makes sense to me that users that incur a large nominal fee have a bigger incentive to compare quotes across different solutions whereas for smaller nominal fees the “convenience factor” prevails. Also CEXs applying a tiered systems seems to support this as I do not expect them to optimize on fairness but on revenue.