See my comment here[0]. Apple added application-level support for non-standard features not supported by SMS. When Apple sends message through the Message application, it selects either iMessage or SMS, based on whether there exists an iMessage connection, and whether the recipient has an iMessage account. This includes for things that are not representable by SMS. Reactions in the Message application, sent to a non-Apple device, show up as nonsense replies, such as "Liked an image", or "Liked 'The full text of the thing you just sent them.'".
[0] https://news.ycombinator.com/item?id=30085322