Only you could deduce that a relay leg from Ryun of 46.9 (47.0 in some sources) was worth considerably faster than 46 in an open 400 on synthetic, and that a 45.5 spit from Coe was worth only 47.2.
You go on to state that Coe was faster over 400 in 78 than 79. Again, showing how ignorant you are.
In 78 Coe ran an open 47.7 on dirt. On that you are correct. I certainly don't feel this is worth 46.7 on synthetic. More like 47.2. But I'll humour you and go along with your 46.7.
In 79 Coe ran another 47.7 on the DIRT at Loughborough in May. On the same afternoon he won the 800m, beating Garry Cook, and anchored the relay in 46.3, faster than Ryun ran his fastest ever split.
"Coe accounted for Andy Kerr with a RELAXED 400 in 47.7, then Garry Cook with a 23 sec final 200 in the 800, and finally had everyone spilling on to the track with a winning 46.3 leg in the 4 x 400 relay" (P.20, AW, 9.6.79)
The relay was won by over 2 secs, so not much drafting there!
If we use your nonsense conversion of taking off a second for cinders, then we get 45.3. Add on the 0.7 from relay to open and we get 46.0. This after already running and winning 2 other events on the same afternoon.
Personally, I feel it was worth more like a 46.5, but I'm playing your rules.
So, we have him running an equivalent 400 open on synthetic of 46.7 in 78, and 46.0 in 79. That is a significant improvement in 400 speed.
Moreover, his 45.5 relay in the European Cup was run after winning the 800 also, and the UK were not last, as you claimed, but 6th out of 8. He had to run around the athletes he beat and was some way behind the 5th place team (0.7). Drafting was minimal and would have been offset by running wide around athletes. His 45.5 was worth 45.5 for a relay and around 46.0 - 46.2 for an open. Again, significantly faster than what he produced in 78.
Your whole way of thinking is alarmingly distorted. Producing a fast 400 time does not mean that said athlete will produce a fast 800m in relation to what they have done before.
For example, in 1980 Coe ran a 1:45.0 and 46.4 400 relay on dirt within 90 minutes early season. That's almost identical 400 speed as he demonstrated in 79. That year he also ran a 3:32.1 1500, again, only 0.1 slower than in 79. With very similar 400 speed and 1500 endurance, he showed have been capable of running another 1:42 low that year. He didn't! His fastest was 1:44.7.
That doesn't mean that was the absolute fastest he was capable of that year. It just means that he never got the opportunity or didn't have the desire/need to run faster! That's the bit you either don't understand, or are just too pig ignorant to admit to; that any given athlete does not always run their fastest capable time over any given distance in any given season.