I've had it make major (with breaking changes) updates to random software when asked to install something unrelated.
HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1 export HOMEBREW_NO_AUTO_UPDATE HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK
I've had it make major (with breaking changes) updates to random software when asked to install something unrelated.