With respect, I think you simply may be overthinking this. The Motu Proprio makes it clear that the rubrics of 1962 are to apply, but that’s about it. It says, if memory serves, that the
obligation (for those bound!) may be met with the 1962 Office. For those of us not bound, I’m pretty sure we are participating as long as it’s a licit Office; the 1962 Office never proscribed laity from using it, it simply didn’t encourage it.
Which means 1962, or LOTH, or any one of the arrangements you might find in a religious community (e.g. monastic, Dominican, etc.) are licit and liturgical. The laity
did participate in the 1962 Office, as public Vespers was quite common on Sundays and big feasts. Mind you that would likely be silent attendance, not actively singing the office except perhaps mentally for the few that would be proficient enough in Latin; others could pray along silently if there was a vernacular translation alongside. Also keep in mind that those in the lay state have always prayed the Office. In monasteries, choir monks not yet ordained would pray it (lay brothers likely one of the Little Offices instead). In women’s monasteries or wherever women religious were bound to choir, they too would pray it aloud and actively, even when no priest or deacon was present.
So the praxis says every bit as much as Canon Law. Maybe even more.
In fact, I always pray compline in the Ordinary Form, partly because it saves time, but mostly because I want to be sure that at least one of my hours is most definitely liturgical every day.
I always pray Compline using the monastic usage even when I pray the LOTH (psalms 4, 90 and 133 said every night,
in directum, i.e, without antiphon). Not because I think it’s more liturgical, but because I want to keep a connection with my tradition even when I use the Roman LOTH, which it has to be admitted, is very convivial for secular use.
I can almost say all of Compline by heart now, at least in French. In monasteries using the original Benedictine schema, Compline was chanted by heart in the dark; it is a very moving and other-wordly experience!
I should point out that prior to Pius X’s reforms of 1910, in France, many clergy would pray a Little Office instead by indult, as the Roman Office was
very long, monastically long in fact (250 psalms per week with obviously many repetitions). But even the 1910 reforms was still too long for many secular clergy, and one of the things the LOTH attempted to address was clergy who simply abandoned praying the Office. And to be honest, our abbey’s schema, 150 psalms per week, I find quite daunting even for an oblate, especially since I sing the Office. Fully sung, the monastic takes a full two and a half hours a day, more on Sundays, feasts and solemnities. The LOTH chops an hour off of that. As a result I find I have much more time to actually
meditate the Hours, with silent pauses, and a slow deliberate chanting. The result is actually a more
beautiful liturgy.
