The option you're looking at only adds or deletes the boot menu option itself, but that boot entry actually tells your PC boot from the exact files that Reflect caches for creating Rescue Media, so to update the boot menu recovery files themselves after you've updated Reflect, launch Reflect and click Other Tasks > Create Rescue Media > Next > Next. You'll be prompted to update your Rescue Media files. Click Continue, then Next again. After the rebuild process completes, even if you do NOT then create any new Rescue Media (which you usually don't have to -- see below), your boot menu recovery files will have been updated. You can also force a manual rebuild of that Rescue Media / boot menu cache at any time, e.g. if you just want to change your BitLocker auto-unlock preferences. The process is the same except you won't get a prompt to update files if there hasn't been an update; instead, click the Rebuild button on the last step of the wizard, then Next.
However, note that there are very few cases where a Reflect update means it's worth updating your boot menu recovery/Rescue Media files. If you read the release notes of Reflect updates, most of them only affect operation under the "real" Windows environment. The way to spot changes that pertain to the Rescue environment is to look for the acronym "PE", which stands for "pre-installation environment" and is itself an abbreviation of "Windows PE", which is Microsoft's name for their highly stripped down Windows environment on which the Rescue environment is based. It is so named because its most common use case is to provide an environment for installing "real" Windows onto a new PC, but a close second is to provide an environment from which to recover
Anyhow, since V7 was introduced, there have only been 2 updates whose release notes mentioned any changes to WinPE at all. Most recently, 7.1.2638 fixed a bug that I reported, but it was minor. And before that, a particular 7.1 release broke Rescue Media completely, so an update to fix THAT was pushed out 2 hours later -- but unless your Rescue Media was built on that one broken 7.1 version, there hasn't been anything critical for PE yet. Technically you could even use V6 Rescue Media to restore V7 images if you really had to. By comparison, back in the V6 days, there were
a few updates that had critical fixes for PE, and their release notes specifically said that users were urged to rebuild their Rescue Media after updating. Again, that hasn't happened yet in V7, though it might soon based on a bug that I reported recently in this thread