Miro does an amazing job to change font sizes when multiple elements are selected and scaled. However, while the font size for changes changes, the font size for labels of connectors stays the same. See here:
It be great if the font size of connector labels would change accordingly.
Absolutely, this becomes more pronounced when elements are copied between miro boards that have established different baselines of scale.
Or even in the same board hen you realise you need to scale up a drawing so that you can add more elements as a smaller zoom scale. You scale everything and it all looks great apart from the arrow labels now become unreadably tiny.
And it also puts a limit on the max scale of a drawing since you cannot make arrow labels larger than 64 which at maximum zoom out is totally invisible.
The connector line thicknesses should also scale so they stay visible as well.