Where are you seeing that?
The install instructions state:
Installation for the Existing Users
If you have an existing installation of Express with Tools, SQL Server Management Studio Express, or Express with Advanced Services, and want to add the complete SQL Server Management Studio feature to your Express instance, do the following:
Step 1: Download the required Microsoft® SQL Server® 2014 Express SP3 file to update your current SQL Server 2014 Express installation by clicking the appropriate link earlier.
Step 2: Run the file, and follow the instructions in the setup wizard to install. On the Installation Type page, select Add features to an existing instance of SQL Server, and select the instance you would like to update.
Note: If downloading using Microsoft Edge in Windows 10, you may be presented with the “Choose Directory for Extracted Files” dialog with a default/proposed path that includes \System32\. If this occurs, please change this path to another location on your system before clicking ‘OK’.
Step 3: On the Feature Selection page, select the Management Tools – Complete check box, and then proceed to complete the installation.
Note: Microsoft® SQL Server® 2014 SP3 Express includes both 32-bit and 64-bit versions. SQLEXPR32_x86 is a smaller package that can be used to install SQL Server 2014 Express SP3 onto only 32-bit operating systems. SQLEXPR_x86 is the same product but supports installation onto both 32-bit and 64-bit (WoW) operating systems. SQLEXPR_x64 is a native 64-bit SQL Server 2014 Express SP3 and supports installation onto only 64-bit operating systems. There is no other difference between these packages.
Now as for destroying your database, it shouldn't, but like with any and all upgrades, you should be doing this on a test system prior to doing it on a live one and you should be testing the changes to make sure nothing breaks by installing the update. ALWAYS ALWAYS ALWAYS do your upgrades on test before live. If you break test, you impact a small number of users and (in theory) you have more time to recover. If you break live, that could be your job on the line.
If you don't have a test system for this, build one as your first step. If live is hosted on a VM, make a clone of the VM and get things up and running with similar hardware configuration but different IP and hostname. If your IT team won't clone the VM, get a fresh VM installed with the same OS and patches then install SQL Server 2014 Express and set it up the same as live and restore the databases from backup. On that note, when was the last time you did a test restore of your databases? A database backup is only known good after a restore.
The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!