I'm sorry, but while I agree Coe did nothing to show he could break 13mins over 5000m, and certainly Aouita would beat him over that distance, to suggest Coe couldn't have run sub 13:30 is ludicrous.
For a start, his father/coach never said that his athlete couldn't break 13:30. I presume you can provide a link that backs up your claim?
Coe had exceptional endurance capabilities. Just because he had a 7:54 3000m pb this does not mean that was all he was capable of!? He ran a handful of indoor 3000m on the appalling wooden 200m track at Cosford as training runs and rust busters in Jan - March. He was AAA indoor champion twice, in 79 and 81. When he ran an indoor 7:54 in 86 his last km was 2:29. Tight bends on a wooden track combined with a 2:29 last 1000m shows he was capable of at least a 7:45 in March.
According to IAAF Scoring Tables, a 7:54 3000m is worth 13:33 for 5k. This was in March and on an indoor 200m wooden track! A 7:45 is equivalent to a 13:17 for 5000m.
Coe also beat Coghlan (83 World 5000m Champion) and McLeod (10000m Olympic silver medalist) in a 4 Mile road race in Ireland (17:54) at the end of '78, off a season running only 800m races! It also broke Brendan Foster's course record by 9 secs. The same Foster who had been the 2 mile WR holder, European 5000m champion and Olympic medallist over 10k. In addition, both Coghlan & Mcleod had run 13.20 earlier in that 78 season, before Coe beat them.
Coe also won the famous Vigevano road race twice (7.5km in 1980 in 20:59, some 38 seconds faster than Ovett was to record winning the same race the following year, & 1983, recording 18.28 for the 6.7km; 27:33 pace for 10,000m).
You mention defeats by Passey (13:20 5k pb) and Lewis (13:21 5k pb), in over distance races, all in the winter & early spring I hasten to add; which has little bearing over ability in peak summer; which is perfectly reasonable for an 800m/miler at that stage of a season. I seem to remember Ovett, who admittedly ran many more road races and X-country than Coe, was also beaten in over distance races by those who wouldn't sniff him over a mile on the track. Yet, you have chosen to totally ignore the fact that Coe beat even more impressive names; Cova, Coghlan, McLeod, Wessinghage (all World, European or Olympic medallists over 5 and/or 10k)in races of longer than 2km. In fact he beat the former 3 in races longer than 5000m.
If Coe's ability was only 7:54 and 14:06, then please explain why he was able to beat 13:20 runners over 4miles?
You should read UK's eminent middle & long distance coach, Frank Horwill's comments about Coe's 5k ability at:-
http://www.pponline.co.uk/encyc/0059.htm.
Horwill states (at the above website):-
"But where did Coe get his amazing endurance from? The answer came to me in 1986 when I went to Battersea Park Track one Saturday morning with a 13:11 5K performer to do a session of 7 x 800 at 5K speed with 45secs rest. The rep times were fixed at 2mins.08secs because the 5K runner was returning to fitness after injury. Coe was on the track and came across and asked what we were doing and could he join in? I felt a little apprehensive that an acknowledged 800/1500m runner would not survive a 5K pace session with a short recovery. The 800s went like this: 2:08, 2:06, 2:04, 2:02, 2:00, 1:58 and 1:56! Coe led them all. Afterwards, he confessed that he did a 5K pace session at 13:20 speed each week. I ventured the opinion that he could run a good 5K anytime. He agreed, but said he didn't like the event! It is doubtful whether any 800m runner before or since could have completed such a session in such times."
The 13:11 5000m performer he refers to is Tim Hutchings (bronze medallist over 5000m at both the European and Commonwealth Championships that year).
I think Coe could have run 13:20 - 13:25 at any time in the peak of any summer with reasonable pacing. If he'd trained for it and stuck to his plans of racing the distance in the summer, then I see no reason he couldn't have got down to 13:10 - 13:15.