This makes it easier to frame or introduce some modalities before introducing
universal quantifiers.

That way, we can use Contractive as part of structure definitions in
which we do not have a bundled OFE yet.

It can be derived, thanks to Ales for noticing!

when using iCombine.

TODO: document this.

Otherwise, the tactic will fail subsequently. Besides, it was inconsistent
w.r.t. the iLöb tactic, which was already doing this.