Of course I know the difference, you clearly do not
Interlacing versus progressive has nothing to do with picture resolution.
1080i sends 1920 x 1080 pixels in two chunks known as fields. In the UK this consists of lines 1 3 5 etc (odd lines - upper field first), followed by the even lines 2 4 6 8 etc.). Each field is transmitted in 1/50 second. In 1/25 second you have a full frame of 1920 x 1080 pixels. The TV will produce this frame in a process known as de-interlacing. All HD broadcasts in the UK now use this system apart from some Freeview-HD content (more later). There may be a 1/50 second between the generated data for each field, this gives the slight jagged edge unless the two fields are derived from the same image as they would be from a movie created from the original film stock. This creates an identical image to 1080p25.
108op25 simply sends the data progressively line 1 2 3 etc. The whole frame takes 1/25 second.
You are expressing a misunderstood myth perpetuating the Sky installers dodgy advice (They aren't Engineeers simply tradesmen taught how to install a satellite dish a task that's not very difficult).
When 1080ps is bandied about they mean 1080p50 which has the full resolution of 1920 x 1080 pixels and the 50 frames/second of 720p50. There aren't any 1080p50 broadcast sources. Many HD Video Camcorders/Digital Cameras and DSLRS can shoot in 1080p50 format (I have 3 such devices).
Deleting a load of video data and then guessing what was deleted is ridiculous.