Tao of Tableau - The Amazing Mystery Tooltip

While I was preparing a series of dashboards visualizing the tides on Panama's Pacific coast for ocean activities planning I came across an unusual situation: one of the visualizations I created has two distinct and separate tooltips, only one of which I put in place. The other shows up and there's no way I've found yet to get rid of it. Here's a stripped down version of the workbook showing this oddity:

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This is a weird little anomaly. The explanation for its occurrence, as far as I can tell is contained in the "The Explanation" dashboard, and follows here:
As near as I can figure out, the mystery tooltip is an artifact left over from the construction of the visualization.

This viz is a dual axis graph, with the left vertical axis presenting the line graph, and the right axis presenting the marks as circles. This is a pretty common technique for creating line graphs with emphasized marks for the actual data points.

The Worksheet's Tooltip, the desired one showing Event, Tide Height, and Tide Date and Time, is configured for the circle graph. The intention is to provide tooltips that expose the desired information.

The line graph has an implicit tooltip, the Mystery Tooltip.
Given the construction on the viz, it is inaccessible for configuration, and presents itself when the user is looking for information.

The line graph tooltips are activated when the mouse comes within range of one of the graph's line segments. This activation range is wider than the activation range of the circle's tooltips, so the line graph tooltip first when the mouse approaches a circle.

This presentation of the Mystery Tooltip is problematic for a number of reasons, the most important being that it's a source of confusion for the person viewing the viz. Sometimes they see one tooltip, sometimes another; this is bad.