@seedfork
Adding the liquid from another daylily (or the liquid from a true lily - Lilium) cannot hurt.
I do not know of any objective evidence that it has made a pod infertile daylily cultivar become fertile. Nor that it has increased the number of pods set for a pod fertile cultivar or that it has increased the number of viable seeds produced from a pod fertile cultivar, etc.
There are many "tips" in the daylily world that many hybridizers believe in and may use but that have never been supported by objective evidence. Most may never have been objectively tested. Most have never been mentioned in published scientific research reports for other plant species. Some
might work some
times in
specific circumstances but I do not think that most have much chance of working. A
caveat - when one works with living organisms one learns to never say never - as soon as one indicates something is "impossible" a report will be published for some species in some circumstances doing just that - the previously considered "impossible".