^^ Yes-
A deeper question is "how much mono would you like?" Or rather, "how low down do you want the stereo difference information to go?" That is directly determined by the spacing between microphones for the entire frequency range, and is the only mechanism responsible for it at frequencies below about 1kHz regardless of the presence a baffle or pointing the microphones so that they have an angle between them. A Jecklin disk baffle begins being effective somewhere around that frequency and higher, at lower frequencies the baffle effectively becomes 'invisible' to sound. Angling the microphones apart from each other is only going to effect frequencies significantly higher than where a baffle starts to become effective.
Perfectly coincident, parallel omnis with no angle between them are monophonic at all audible frequencies. As the microphones are moved farther apart, stereo difference information begins to manifest above a decreasing point in the frequency scale, in direct relation to the spacing. At the very lowest frequencies, even very widely spaced omnis are still effectively monophonic. Near-spaced omni techniques like Healy and Jecklin are monophonic up to much a higher frequency. Jecklin is effectively monophonic up to somewhere in the midrange. Compared to non-baffled parallel omnis with an otherwise identical spacing, Jecklin baffled omnis will produce greater stereo difference information at all frequencies above that point. Healy, with the same spacing is going to be monophonic to a higher frequency than Jecklin (but may sound 'airier' way up top).
There are other things going on too with changes in spacing, but this aspect is a basic and important one.
Where is the appropriate mono to stereo frequency break point? It all depends. For a recording of an orchestra or an audience recording of an amplified band, I prefer to have stereo difference information down to a lower frequency. As long as the other aspects are kept well balanced, that sounds bigger, wider, open, more natural and just better to me than a narrow spacing. But for something like a solo piano recording, the technique John mentions above using 20cm spaced omnis is going to be far more appropriate and natural sounding. For a close shared vocal mic, where the intent is to place the vocals solidly in the center of the playback image, a mostly all monophonic recording with perhaps a bit of added air and space up top from using x/y omnis could be entirely appropriate.