The problem is that we don't know when the plans changed. The 12c showed up on the slides in January when vendors were first seeing R7 final silicon. Rumors of the TR hit us in mid March. So maybe even earlier for Intel. So if MCC was already being tested prior to January and sometime in Q1 they changed their plans. Then all of sudden its 6-9 months and not 4. Half a year sounds about right. Remember AMD didn't get Ryzen to Mobo companies till a week or two before the Chinese new year.
You seemed to be focused on the the fact that the because Intel released different products the slides were wrong. When to a lot of people which includes the motherboard manufacturers its seems like they ended up being wrong because Intel released different products. Or better put that the slides were right till Intel decided they needed to change the lineup and not that they were off the entire time.
As for TR vs. SL-EP vs. SL-X. The Xeon lineup isn't competing (though it can compete) in the same market as TR and SL-X. SL-X and TR are about high performance desktops. Not "workstations" and not server work. AMD if they wanted to could fill most of the market just like you are saying with the Xeon lineup with EPYCs. If the rumors are right even the 8c EPYC would still offer great margins. So they would just need mobo companies to make a Desktop SP workstation board. But TR is about performance on top of core count. It has aggressive clocks to match their lower core count brethren which they couldn't do with EPYC. This is what SL-X is about competitive clock speeds using an enterprise chip. These are High performance platform which mean they need to be the jack of all trades. The fact that they didn't know and where still trying to figure out TDP and clockspeeds after announcing the product should tell you that. Which goes back to point 1 that considering the three major points. 1. No reference to the CPU's in the roadmap, 2. The surprise by the mobo makers of their existence. 3 That the specs were not finalized even though they had been producing the chip for a while in the form of SL-EP, that it is more likely than not that their inclusion in the x299 launch was a newer development and not that Intel was always planning it but wasn't ready yet.
Just like today's announcement probably has more to do with Threadripper being days from being available with chips with 60% more cores and Intel needing to tell everyone to remember that they have the 12c+ stuff still coming.
Thats the whole point here, we dont know when the plans changed or if they changed at all, why 12C appear out of howhere before Ryzen launch? 8C Ryzen was all that was know at that moment, with no idea of price or performance, that was no reason to increase core counts. At this point both sides could be right, but there is not hard evidence to support either.
Lets look at TR.... what we know about it? TR was announced before Computex, and the only thing they said is that it was 16C max, in fact until recenly we knew a lot more of SKL-X unreleased SKUs than of TR.
To me it looks more like both were trying to keep their best SKUs specs until last moment, and actually that exactly what happened as Intel released their specs just after AMD.
About point 1, as i said, slides could be worng, slides could be changed, specially if those are pre-announcement.
About point 2, im not sure there was a suprise at all by mobo makers, i think that was said because of that one guy of one of the oems that said SKL-X 18C was 2018. he was wrong. Also if you are going to increase core count overnight you are going to warn OEMs about it, specially if there is a presentation coming.