Without any pattern specified, the code you posted will accept emojis as input, it's not a good choice for a numeric only field. It's also intended for phone numbers...
Woops, for some reason I read the title as "Why the GOV.UK Design System team changed the input type for phone numbers" - removed my comment since it doesn't apply.
Without any pattern specified, the code you posted will accept emojis as input, it's not a good choice for a numeric only field. It's also intended for phone numbers...