Although that might make the trunking bigger than it needs to be even for sheathed singles, and enforces a proper complete run of trunking from end to end. Using sheathed cables allows a certain amount of flexibility in the awkward angles and crevices that it sounds like the cables need to negotiate. The trunking can be used to hold them in position without having to be 100% continuous. OTOH you might get better CCC with singles if it matters.
On a side note I think 'meter tails' is a misnomer here. Surely meter tails are specifically the cables from head to meter and meter to isolator. This is a distribution circuit, part of the installation and no different to any other circuit, even if it is installed using a type of cable most often seen used as meter tails.
And on a vintage note, if the old TRS rubber distribution circuit is being pulled out, I would be very keen to get hold of the old cable. It is proving very hard to find usable samples of heavier TRS cables that can be formed into shape in a display. Smaller cables we have good lengths that are still supple but anything 7/.044 and up is a problem. I will happily exchange it for beers if any good runs can be saved.