incoming group message not showing in Usage

This started recently. My wife is in a group text with her friends. She has Galaxy S9+ while her friends use iPhones. They are also with other carriers (I think Verizon). Before May 8th, all incoming text messages from that group text were appearing in Usage. All of a sudden, after May 8th, only her outgoing messages to that group text appeared in Usage. What's more weird is that individual incoming text from either friends are appearing in Usage. And I think I see this from other group texts that she has with family too! Basically, incoming text from a group text is NOT appearing in USAGE but her outgoing text to that group is appearing. incoming individual texts, however, do appear, even from people from other carriers and iPhones. My wife uses Messages and her friends use iMessages. not any chat apps like Viber or Whatsapp or FB Messenger. I know those go through internet as data. i'm talking about text messages.