providing an arbitrarily non-reduced fraction is an even sillier alternative. the same fundamental issue arises either way, and it’s much clearer to use obvious semantics that everyone can understand

sure you can, you say “i need a hole with diameter 0.25” ± 0.015625“”. it doesn’t matter that you have more sig figs when you state your precision

but regardless, that’s probably not the precision you care about. there’s a good chance that you actually want something totally different, like 0.25±0.1”. with decimal, it’s exceptionally clear what that means, even for complicated/very small decimals. doing the same thing fractionally has to be written as 1/4±1/10”, meaning you have to figure out what that range of values are (7/20” to 3/20”)

i’ve never heard of anyone using non-reduced fractions to measure precision. if you go into a machine shop and ask for a part to be milled to 16/64”, they will ask you what precision you need, they would never assume that means 16/64”±1/128”.

if you need custom precision in any case, you can always specify that by hand, fractional or decimal.

how does this compare to mermaid or plantuml?