Tooltip is missing for Add (+) button in Particle system.

In the particle system, under the Renderer parameter, for Mesh Render mode, the Tooltip for Add (+) button is missing in the inspector window. Refer attached screenshot.

Steps to repro:
1. Create a New Project.
2. Hierarchy > Effects > Particle system.
3. Particle System > Inspector > Renderer > Render Mode > Mesh
6.Observe tooltip is missing for Add (+) button

Actual result:
Tooltip is missing for Add Mesh (+) button

Expected result:
Tooltip appears when the mouse has hovered on the properties

Reproducible in:
2021.2.0a16, 2021.1.6f1, 2020.3.7f1, 2019.4.25f1, 2018.4.34f1

Note: Tooltip appears for similar add (+) button in Game View tab for free aspect add button

Environment:
Occurring on Mac 11.2.3 and windows 10