Microsoft Excel Remote Code Execution Vulnerability

According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
An attacker must send a user a malicious Office file and convince them to open it.

Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.

According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?
The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally.
For example, when the score indicates that the Attack Vector is Local and User Interaction is Required, this could describe an exploit in which an attacker, through social engineering, convinces a victim to download and open a specially crafted file from a website which leads to a local attack on their computer.

Security updates
16.0.10417.20128 — https://support.microsoft.com/help/5002871
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.109.26051019 — https://go.microsoft.com/fwlink/p/?linkid=831049
16.0.5552.1000 — https://support.microsoft.com/help/5002865