I doubt 40k people have their IELTS just sitting around unless they were already anticipating applying for CEC, when I got my test back in November, we were like 50 people (full capacity) per day.
I personally asked my employer to post-date my job letter, but I think that as long as you have a fairly recent job letter and some pay stubs to support your application you should be fine. Don't be afraid to submit too additional documents to prove your eligibility, some people argue that it might delay your application but the truth is that this is a legal process, you're the one that has to prove you're eligible.
If the officer considers 2 of the 4 "work experience" documents you submit are enough, they won't bother looking at the other ones. But if they need additional evidence, they will ask and take their sweet time reviewing your documents. Don't do the bare minimum, make your application as perfect as possible in a way that even the dumbest person on earth could see at simple sight you're eligible.
I really like the wording in here "Accelerated" suggests short processing times, if this isn't just IRCC fluff, then it might be the reason why they won't issue BOWP for these streams. It could also refer to the fact they don't make Into graduates wait for their full 1 year of work experience though, but then it doesn't make sense for essential workers and francophone streams.