I think the people you are talking about are referring to fiat in general and not just dollar. If all currencies are getting weak at the same time one of them is still going to be the strongest and Dollar remains the strongest currency there is. And having a higher value doesn’t mean that a currency should be the strongest, if that’s the case then I don’t think that even the Euro stands a chance in being among the first three because there are other currencies with more value than the Euro and USD respectively
That ultimately depends on the total supply of money and the size of the economy
As you say, a higher exchange rate doesn't necessarily mean that a currency is stronger. It just means there are fewer currency units in circulation given more or less the same size of the economies compared. To gauge the strength of a currency we should look at its dynamics, i.e. how its exchange value changes over time. So if a currency with a higher rate loses its value (depreciates stronger and faster than other currencies), this rate should go down too even if technically it may still stay above the parity
Higher exchange rate doesn't necessarily mean that a currency is stronger. However it shows that currency is usable for more people than other currencies and that means more value compared to others.
And that value can lead to price pump
