I spent the whole day thinking about what were the reasons behind this unprecedented increase in the number of ITAs. I believe it's either:
1. To compensate for the B2B draw that should have happened in the last week of January, they decided to split these 3400 ITAs that would have been given, and today's and next 2 draws will have +1000 ITAs than the usual.
2. Maybe CIC was not expecting such increase in the number of candidates in the 450-600 range, and realized that Canada could benefit from these immigrants in the 465+ range that are currently being ignored. When the cutoff was fluctuating between 440-450, they really didn't have to pursue the candidates in the 430 range, because most of them didn't even had CLB9, they simply were not an asset for the Canadian economy. Maybe it's a crazy ideia, but I wouldn't be too surprised if they release a new target for 2020 in the coming weeks, to accommodate highly skilled professionals that want to immigrate, but are not being given the chance.
3. They're planning FST for next week, but do not want to see the usual spike in the CRS cutoff that post-FST draws usually get, because that would frighten very qualified outland candidate, that wouldn't be able to beat a +480's cutoff reality. That could easily turn EE into an inland process (pretty much just like almost all PNPs programs that required job offers).