Users & Unique Visitors numbers are identical

Both numbers from our page are identical.
Can it be correct, even though we know, that users with respective user ID ( set via setUserId) enters our page on two devices, Laptop and Smartphone, and thus uses two different browsers?

FAQ says:

Unique visitors are determined using first party cookies stored in your visitor browser. When a same person visits your website on two different devices (for example their laptop and on their mobile phone) then Matomo (Piwik) will detect two unique visitors.

@SteveG , could you help, please?

I would assume that using the user id feature changes the unique visitors detection. So a user with the same id always only counts as one unique visitor, regardless how many devices or browsers he is using.
The FAQ describes the “normal” behavior, where it is not possible to know that it’s them same user on different devices.

@SteveG , so I don’t understand: Users vs unique visitors (not equal) - General questions - Matomo forums

This might also depend on the config setting of enable_userid_overwrites_visitorid, which should be enabled by default.

@SteveG , thank you for your reply.
Our problem is we track two different systems in one Matomo and
platform 1. has different numbers of unique visitors and users
platform 2. has exactly the same number of both KPIs

for both platforms:

  • implementation of setUserId is very similar for both platforms. We take the user ID saved in localStorage;
  • UserId for platform 1 and platform 2 is the same in two different browsers, Chrome and Firefox;
  • config setting of enable_userid_overwrites_visitorid is the same, because it’s the same Matomo;

but only platform 2. has the same number of unique visitors and users.
What else could play a role here?