I checked the tooltip rendering across all suites and it differs because of some suite-specifics (the main differences are described in this issue -> https://github.com/telerik/kendo-themes-private/issues/187 ). Also, I had a discussion for the chart tooltip with @nstoychev and it appears the chart tooltip does not use the Tooltip component itself (because it could not be absolutely positioned and the chart canvas rendering). Therefore my suggestion is to keep the chart tooltip rendering as is at the moment and apply the suggested css rules.
I checked the tooltip rendering across all suites and it differs because of some suite-specifics (the main differences are described in this issue -> https://github.com/telerik/kendo-themes-private/issues/187 ). Also, I had a discussion for the chart tooltip with @nstoychev and it appears the chart tooltip does not use the Tooltip component itself (because it could not be absolutely positioned and the chart canvas rendering). Therefore my suggestion is to keep the chart tooltip rendering as is at the moment and apply the suggested css rules.