I can give a guess. There are some companies that sell the leachate as worm tea. I expect that leachate and brewed tea from castings are not going to be the same. That probably doesn't mean that the leachate is bad but it probably does not have the same nutrient value. Fresh leachate may still have a population of beneficial microbes that could help your garden. Worm tea that is sealed in an airtight container or kept around for too long is going to loose the benefit of the living beneficial microbes found in fresh worm tea. This would make them not as good as fresh but they will still have the nutrients from the castings provided they are brewed from castings and not just leachate.

A good healthy wormbin will not have a bunch of leachate. If the leachate is from a unhealthy situation in the bin it will not be good for the garden. If the leachate is from a unhealthy situation you may not know it for a week or two till the worms start dying. If you have a small amount regularly I would pour it back in the bed. If you have a bunch all of a sudden you need to find out why quick!

yes, leachate is simply the result of poor bin management - and like immature compost it will contain phytotoxins that will not be good for a variety of susceptible plants .... totally different thing than a tea, which yes, should be used immediately, as it should be an areated tea containing beneficial aerobic bacteria, and sitting around lets it get anaerobic .... people sell anything they can get others to buy, doesn't mean it's good or even what they say it is

Bill