I have just made the assumption it's changed since GDPR maybe( purely supposition)? Never used to get them now like I said I'm getting them for ages in advance for some reason. I've also had two essentially identical ones arrive this week for my LGW-SVQ trip this Sunday just formatted slightly differently but giving the same information without any additions in one over the other.

While they invoke fear & loathing the seat change email is nice to see as I've had them happen and only found out by chance so it's nice good to see that they seem to be becoming more proactive in alerting people to them. The one on the image worked for me whereas another recent one that didn't wasn't communicated at all so maybe they have decided they only want to let you know if said change will probably make you happy not annoyed.