Removing the foliage on either has no effect on flowering. Typically, bearded iris foliage remains more or less in place all winter, although some folks do cut it back (but not off). With the daylilies or with species iris, you can cut back the foliage whenever it starts looking too ratty.

I think the idea is to let the leaves produce energy for the plant as long as possible, then clean up the brown or yellow leaves to prevent pests from setting up shop. I cut my daylilies down when the leaves have turned yellow, and I wait longer on the irises. I cut them down to 3 or 4 inches after three or four hard frosts.

Removing foliage on perennials really has no bearing on their ability to produce or store energy - if damaged or diseased, it can typically be cut back to the ground without issue or harm to the plant at any time during the growing season. And many times advised. It is the health of the root system that governs the ability to store energy and produce healthy growth and flowering in following seasons.

If dealing with bearded iris, in many mild winter parts of the country, the foliage is not removed or cut back in fall at all as it is essentially evergreen. OTOH, most species iris foliage is deciduous and can be cut back to the ground when its appearance demands it. Or when it is convenient to the gardener :-))

It’s my understanding leaving green leaves until they’ve yellowed allows plants to continue feeding their roots, corms or bulbs.

Corms, bulbs or tubers are treated quite differently from regular mass rooted perennials and those do need to have the foliage left in place to ripen and re-energize the bulbs for the following season. Herbaceous (or mass rooted) perennials do not require the same treatment. The roots are always present (not the case with bulbs or bulb-like plants) and the energy necessary for regrowth is always present as well, as long as the roots are allowed to remain healthy. With herbaceous perennials, it is the roots that feed and support the top growth, not the other way around ;-)) One can cut back perennials at any time during the season you like for varying reasons, often to removed diseased or disfigured foliage. If one had to leave all foliage in place through the end of the season until it died off naturally, deer-ravaged plants like hostas would never survive more than a season!!

OP asked about irises (rhizomes) and daylilies (tubers). Everything that I've read counsels against cutting the foliage down too early. Gardengal48, I'm a little confused here!

Not all irises have rhizomes and daylilies are fleshy rooted perennials, not tubers.

I am a zone 5/6. I do not cut anything that is still green. I have been able to kill any plant including aggressive weed by removing the foliage. I have always believed the green above feed roots, bulbs, rhizomes and anything else that is below the ground.

I can see a higher zone have a longer growing period therefore the opportunity to have given a plant a longer period to store energy than a plant grown with a shorter growing season to store maximum strength.

No scientific proof for my belief just the way I garden. Green stays, Yellow cut.