We use the --all-features flag because some crates don't produce an executable unless we specifically use the --feature flag.
We couldn't find an easy way to determine what features produced an executable, so decided to use --all-features directly.
What you hypothesize is actually true.
We notice some errors were due to us using this --all-features flag.
In a future update, I will write a resolver which will resolve and use the correct feature flag automatically.
But that's far in the future.