They've probably trimmed it down because they have dug it up and divided it off a larger clump, and trimming it down is the right thing to do when you damage the roots by doing that. If you plant it in the ground and then dig it up to divide it later, you yourself will be doing damage to it, and thus lose some of the benefit of the growth to that time. On the other hand, you need enough of it to make simple divisions you can just fling in the ground and expect to live - small divisions need more sophisticated horticulture to get them to take.

If there are new shoots coming up at the moment, then don't do it now, you'll probably lose the new shoots and set the plant back significantly. Wait until the autum. Autumn is probably a better time for major divisions than spring, because root damage is repaired over the winter. (Minor divisions, root cuttings, carefully cultivated in greenhouse, I am told are best done in Feb.) If it isn't shooting yet, and you have at least 8 culms and can carefully split it in half, then go for it and do it now, (and at 90 squid I would hope they have given you that much).