Then turn it around, it is a bug still then because all or (some) of your other V5 end points return it as int… I just noticed this, because featured was the only one returning it as a string, all others not.
https://api.twitch.tv/kraken/search/channels/?query= does return it as int.
https://api.twitch.tv/kraken/users?login= does return it as int.