Flutter textFormatterList blocks Alphabetic characters

Question

In my flutter application I have a field to enter users name.

I only want to allow English, Japanese letters and space in there.

I use following formatter to allow those fileds.

 textFormatterList: [
    FilteringTextInputFormatter.allow(
       RegExp(r'[\u3040-\u30ffA-Za-z\s\u4e00-\u9fa5]')),
],

On Android devices there is popular keyboard called "Gboard"

https://play.google.com/store/apps/details?id=com.google.android.inputmethod.latin

When I use this keyboard and switch to English letters I am not allowed to enter English letters.

when I press letter 'a' in the keyboard the unicode value is u61.

This seems to be within the range, however it is getting blocked.

Any idea what is happening here?