Regardless, the wedding and reception behavior was entirely irresponsible. But the link between it and the long-term care cases seems tenuous, at best.
https://www.cdc.gov/mmwr/volumes/69/wr/mm6945a5.htm
It looks like just contact tracing here, not genome sequencing.
The patient in question is A2 and the study does not say whether they ever tested positive or had symptoms.
Everyone seems to say "1-2 days before symptoms start", although some sources say "2-3 days". And yes, as you say, the 2-14 days for becoming symptomatic seems to be much more agreed upon.
That's where it seems to me to be a very rapid spread (below average) from the wedding to the LTCF. But not impossible.
I was also curious about the situation around the LTCF in the days leading up to that outbreak. I was expecting to find that perhaps there were other community cases around there that could have contributed to the LTCF.
However, looking at the MeCDC website for Somerset County (where the LTCF is reported to be located), the county seemed to be pretty "under control" in the days leading up to this event. The most recent confirmed cases had been over 2 weeks prior, on July 24th. It's actually the longest they had gone without a new case in almost 3 months.
Given that, I'm more likely (as the CDC concluded) to suspect the contact tracing from the wedding to the LTCF as being the cause. It's not an absolute link, but it's probably more likely than I originally assumed.
Edited