You've told InDesign to insert a tab when it creates the listing. That's NOT the same thing as defining the type and position of the tab in the paragraph style definition. That said, in my testing failure to define the tab stop results in ID using the default tab stop at .5 inch. The only way I was able to create a collision such as you've pictured was to use a center-, right- or decimal-aligned tab instead of a left-aligned tab in the definition, or to set my left-aligned tab too close to the numbers.
Something wrong was happening here because the TOC sometimes mixed items an numbers but it depends on your advice (type and position).
It seems is not a bug at all when the results are those shown in the picture.
Perhaps a limitation is that any update to TOC will require to insert the tab before the page number.
Thank you, very good information as always!
Europe, Middle East and Africa