You don't NEED a new dipstick. However, if you have a Q50/Q60 built before mid-year 2019, you CAN install the shorter dipstick, add the extra 1/2 qt of capacity to the sump, and be on your way.So unless you are getting your entire long block or short block replaced, you do no need a new dipstick.
Note: The existing Rev A dipstick for the 2016-early 2019 MYs has been discontinued. Along with the Service Bulletin, it indicates the VR30s across ALL years (2016-2020) will now be spec'd for Rev B (shorter length) dipstick. Thus being shorter, it's measured MIN/MAX range provides an extra 1/2 qt capacity.
Why this change? Infiniti supposedly discovered the some of the engine/turbo seal failures were due to oil starvation, and adding a 1/2 qt to the sump level will help address this issue. Is it the be-all, end-all solution, especially for the turbo seal failures? Likely not, but if Infiniti allows an extra 1/2 qt for reliability of the wetted internals, and the engine can handle the extra 1/2 qt of capacity, to me it's a no-brainer to make this change for about $30ish dollars.