The fact the the tooltips close automatically regardless of the HideEvent setting (unless it is ManualClose) is by design. This behavior is controlled by the AutoCloseDelay property, which has a default value of 3000ms. This is explained in this help article
If you want to avoid this automatic closing (which is also exhibited by tooltips in the OS or the browser) you can either set the AutoCloseDelay to a high value (to keep the behavior, but just delay it), or set it to 0 to prevent it. You can test this in the First Look online demo
The HideDelay property is the one that is used for controlling how long after the mouse moves away from the target the tooltip will hide. This can also be seen in the First Look demo. Of course, if another tooltip must be shown the previous will hide immediately, regardless of this setting.
I hope this clears the your questions and doubts.
the Telerik team
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