Steps to reproduce the issue

I am adding list-fancy-select layout on a sql field as:

<field
    name="sqlmultiple"
    query="select id,title from #__content"
    key_field="id"
    value_field="title"
    multiple="true"
    type="sql"
    layout="joomla.form.field.list-fancy-select"
    required="true"
    label="COM_TENIS_FORM_LBL_ASDF1F_SQLMULTIPLE"
    description="COM_TENIS_FORM_DESC_ASDF1F_SQLMULTIPLE"
    hint="COM_TENIS_FORM_LBL_ASDF1F_SQLMULTIPLE"
/>

Expected result

When I select multiple values to be displayed as selected

Actual result

The values are stored in db but aren't selected

System information (as much as possible)

PHP Built On Linux 39f2b7fe885b 4.19.128-microsoft-standard #1 SMP Tue Jun 23 12:58:10 UTC 2020 x86_64
Database Type mysql
Database Version 8.0.23
Database Collation utf8mb4_general_ci
Database Connection Collation utf8mb4_0900_ai_ci
Database Connection Encryption None
Database Server Supports Connection Encryption Yes
PHP Version 7.4.16
Web Server Apache/2.4.38 (Debian)
WebServer to PHP Interface apache2handler
Joomla! Version Joomla! 4.0.0-beta7 Beta [ Mañana ] 2-February-2021 19:23 GMT
User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:87.0) Gecko/20100101 Firefox/87.0

Additional comments

I have debugged the $value variable that goes to layouts\joomla\form\field\list-fancy-select.php, It is a string.
Seem that it needs a conversion as I see here libraries\src\Form\Field\TagField.php:

if (\is_string($this->value))
{
    $this->value = explode(',', $this->value);
}

Could it be considered as a bug or list-fancy-select can't be used on all field types?