RPL took 2.5 years of dev time. ADL took 3 years.
MTL taking 2-3 years of dev time is essentially the same time it took for RPL from development to launch. Using RPL timeline as a template for this debate is perfectly acceptable.
Also, MTL has been confirmed to launch to Q3 this year. MTL's tape in, tape out, and power on dates have all been announced by Intel themselves. Its timeline fits. I'm not making this stuff up, literally search up the individual events and dates if you want to yourself. Sure, chiplets in theory might shrink down design timelines, but with MTL, it appears to have taken a similar amount of time as RPL/ADL.
MTL literally was not design ready for a late 2022/early 2023 launch date. Idk what to tell you. Pat also mentioned that MTL will PRQ in Q3, so that would mean the time between PRQ and power on would be still ~15 months. That means MTL spent around the same amount of time in post-si validation as RPL did (slightly more actually). Intel has been announcing engineering milestones, it all lines up.
Plus Exist50 (god bless his banned account lol) has been complaining about MTL's design woes for a while on this thread. It apparently wasn't smooth sailing.
Gelsinger and the CFO both said in the recent earnings call that MTL was launching/PRQ in Q4. Then, like 4 days later Gelsinger said it was Q3. Seems like they made a lot of progress in those 4 or so days. I think it’s likely we see essentially a paper launch in Q3 with actual ramp starting Q4 based upon this but who knows, we’ll see soon enough.