The idea of PLP Monitoring or Preferred Landing Monitoring is the action of ensuring the correct (the specific page that was created and optimized to convert the best for a specific query, audience, market, or campaign is the actual page that is ranking the highest.
We have found that replacing “any ranking page” with a specific PLP can lead to as much as a 50% improvement in conversions since the page is more relevant to what the searcher is looking for. This is critical in local markets to have the correct page.  Imagine the frustration of an Australia searcher clicking a search result and being brought to a page in the US or UK that has a different currency and not likely able to ship.
It is not uncommon to have older pages or totally random pages that outrank the desired page. By monitoring key pages you can identify where the best page is not the page you want and make changes. If it is the wrong market use hreflang, an old page set a 301 redirect, and if a less optimal but necessary page add a canonical tag.
For a UK-based travel site that was ranking #1 and getting around a 50% click rate on a specific keyword but was not getting any conversions. Quickly looking at the page we found “last years” offer page with no current offer resulting in a 98% bounce rate on the page. A simple 301 redirect was added resulting in $60k in new revenue in 10 days. ? This is revenue that would have been lost had they not identified that the desired PLP was not the page that was ranking.