do you know if there are instances in the past where we've made an exception and introduced a change in a minor version?

No I don't recall. Since v1 we tried to introduce breaking changes in major versions only.
At the moment there is another PR (#7675) merged to the master which could/should considered a breaking change i.e. related to bars with text.
In addition you may also include the following PRs and issues to release v4:
#7696, #7692, #7680, #7536,
#7623, #7598, #7174, #7026.