Multi-value term field bypasses Force Deepest Selection requirement

I've encountered an issue when selecting multiple terms, for example, with IDs 2 and 3, using the Simple Hierarchical Select (SHS) widget. The form field value for these selections is concatenated into a single string: '2 3'. This format seems to be directly influenced by the cardinality setting of the field. Specifically:

When the field's cardinality is set to allow only a single value, the expected format is a simple string or integer representing a single term ID.
For fields allowing multiple values, it appears there's an expectation for an array of IDs. However, SHS concatenates multiple term IDs into a single string.
To align with the expected data format, especially when handling multiple selections, I propose a temporary adjustment to the data shape by splitting the string based on spaces:

if (is_string($value)) {
  $value = explode(' ', $value);
}

This modification would transform the concatenated string '2 3' into an array [2, 3], making it consistent with the expected input format for fields allowing multiple values. The current handling inadvertently wraps the string into an array like [2 3], which leads to validation errors.