We don't use his old 800m time to evaluate his speed/muscle fiber ratio. But we saw dozens of races of him and it's always the same vs other good runners with more speed - he gets smoked/destroyed on the last 100-200m. Especially in slower races, like the European Indoor Championship 2019 1500m. But even in Doha, which was a fast race.
Runners can have a strong 800m time without being very fast-twitch, just by being extremely strong aerobically. Klosterhalfen is a similar runner to Ingebrigtsen - lots of endurance, stamina, but no strong sprint finish. Yet she ran a 1:59 - which is probably equivalent to 1:44 or so.
So even if Jakob runs a 1:43 or 1:44, as you or some other people think (in my opinion it's not even guaranteed), as long as he keeps getting outsprinted at the end of competitive races we won't consider him a "speedy 1500 guy" or "FT runner in 1500".
And the argument "but he closed a race in a 53!" also gets old. Lagat closed a race in a 52-second lap as 41-year old. He never broke 1:48 in the 800. So Lagat is now a speed monster? Closing a long-distance race quick is more of a sign of supreme aerobic ability, as in "there is a lot left in the tank at the end" rather than raw, sprint speed.
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You state that Jakob gets smoked in the last 100-200m in dozens of races!
Will you please
A. Watch the following races
a. 1500m Palo Alto 2018
b. Bowerman mile 2018
c. 1500m Monaco 2018
d. 1500m Stockholm 2019
e.1500m Lausanne 2019
f. 1500m Monaco 2019
g. 1500m Brussel 2019
And tell this forum if you want to moderate your statement?
B. Will you also tell this forum how many times the excellent finishers Centro and Engels have beaten the slow 17-19 years old Jakob?