On restrictions on String variables used for 'Grouping Valiable' of 'Independent-Samples T test'

About 'Grouping Valiable' of 'Independent-Samples T test'.
Improvement request
I would like to use Long String (eg 24 bytes) as 'Grouping Valiable'.

In the case of String variable, only variables that variable width is 8 or less can be input to [Grouping Variable].
If you use a variable width of 8 or more, the following warning will be displayed.

Warnings
The GROUPS subcommand specifies an unknown variable or a long string variable.
This subcommand must specify either a numeric variable or a short string variable.
Text found: variable name

The description of OnlineHepl has the following description.

https://www.ibm.com/support/knowledgecenter/en/SSLVMB_25.0.0/statistics_mainhelp_ddita/spss/base/idh_ttin.html
Independent-Samples T Test

Data. The values of the quantitative variable of interest are in a single column in the data file.
The procedure uses a grouping variable with two values to separate the cases into two groups.
The grouping variable can be numeric (values such as 1 and 2 or 6.25 and 12.5) or short string (such as yes and no).

Currently, 'Grouping Valiable' can only input Short string. I would like to use Long String (eg 24 bytes) as 'Grouping Valiable'.

When the character code is alphabet (ascii)
If the character width is 8tytes, meaningful contents can be expressed.

In case of character code, Japanese (UTF-8)
If the character width is 8 bytes, only two characters can be used.
With 2 characters, it is difficult to express the content, so we request improvement of the specification.