Kees
Ok, just to be sure I am not theorising a non practical situation, I did some tests with a piece of curly maple.

Plane is a Stanley #4 with a Ray Iles iron.

First a wide open mouth and the capiron pulled far away from the edge. Big and deep tearout was the result.

Then closing the mouth to something that passed a 0.10mm feeler gauge. When taking very fluffy shavings I could remove the tearout, but with a 0.7mm shaving there were still some spots with tearout.

Finaly, setting the capiron at 0.2 mm and opening the mouth again, everything was fine again, even with 0.1mm thick shavings. 0.15mm shavings made new (fine) tearout again.

Conclusion, yes a tight mouth works, but not as good as a close set capiron with a wide mouth. And closing the mouth to such a thin slit is realy fumbly on a Bailey plane! Especially because you can't reach the frog setting screw very well with a scredriver. The tote is in the way.

As always, take my fumblings with a shovel of salt. Experiment for yourself.