Hello Dmitry Goncharov

Please share steps to find the issue. What is the Joomla version and where to check for the issue?

Best regards

Add additional fields to the user during registration. And you will see that variables pop up.

Jooml 4.0.4 HU 2.0.6

Please override the language string and change the value. Go to this location: language/overrides and take a en-GB.override.ini file. Then translate this language string COM_USERS_OPTIONAL="Optional"; Use your language prefix instead of en-GB (en-GB is used for English language).

Is this a template bug? Will the update be fixed?

If site language is set on English and this works, then it is not considered as a bug. It probably occurs because of different site language.