That's what I've been saying all along, but got shot down in the other thread when I tried to say Intel has a massive lead in ST performance.
Agreed that you are being conservative on all 3 points though.
IPC difference seems to be greater than 6%, easiest way to see this is to look at single threaded benchmarks or completely CPU limited gaming scenarios. I would say it is 10% - 20% depending on the application (please, AMD fans, don't start a flame war about this)
https://www.cpubenchmark.net/singleThread.html (compare 4770K to Ryzen, Haswell has superior single thread performance)
https://tpucdn.com/reviews/AMD/Ryzen_3_1300X/images/perfrel_1280_720.png (CPU limited gaming chart, compare the 1300X to i5 7500, both 4C/4T chips @ 3.4GHz)
Max O/C: If motherboards like the AORUS have a 5GHz 'auto o/c' function built in, and all reviews/leaks so far hit 5GHz+, we can probably say 4.8GHz is a conservative figure.
With regards to threads/SMT, AMD actually gains more than Intel from SMT here. If you look at the ST to MT scaling in Cinebench or CPU-Z benchmark this is obvious to see.
So whilst your maths is rather conservative on all 3 fronts, I do agree with you as a whole, Coffee Lake will provide comparable MT performance whilst having a big lead in ST.