Whatsapp - “you may have new messages” - but don't receive any [on hold]

I've received the "you may have new messages" notification a few times on my Nexus 5X due to the use of data saving, however, this evening I received the notification once again, but when I opened WhatsApp, no new messages came through like they normally do. I understand that the use of the words "may have" imply that I might not have necessarily received any new messages, but I find it strange that such a notification would appear if I hadn't received any new messages. Has anyone else experienced something similar, and does anyone know why the term "may have" instead of "have" is used?