I am using eM Client 7.0.26861.0 and just discovered this problem. Booked a flight and the the data was added to my iCloud calendar but didn’t show up in my eM Client. I discovered when I deleted the URL field in the iCloud calendar and repaired the connected iCloud calendar it suddenly appeared. The URL field had something like “message://xxxxxx” and was linked to my confirmation mail by the airline.
using 7.0.27943.0 and just had the same problem. seems like this is not fixed. please put on the to-do-list.