This is not new. I remember Dave explaining, a year to two ago, that there had to be a limit on the number of search results, although I haven't been able to find the particular thread where the discussion happened.
Anyway, as zuzu has pointed out a couple of times, if you want to see all 13,000+ cultivars of Tropical Hibiscus, there are far more efficient ways to go about it than typing "Hibiscus rosa-sinensis" into the search box on the Plants Database page. If you go to the custom database for Tropical Hibiscus and click on the "browse the full list..." link at the top of the page, they will all be there, in either alphabetical order or by popularity, whichever you prefer.
https://garden.org/plants/brow...