Just two comments.
First, I think it more likely the pressure on the PL came when the leaks came out. Pressure to start the investigation. Once started, the PL has had to see it through to the end and, if they haven't seen the evidence to counter their allegations, then they have to refer at some point.
Second, I am still struggling to see how the PL would think referring City to an IP for such serious charges and giving two other clubs points deductions (one twice) is going to stave off an IR. It has been a complete shit-show which just proves the exact opposite. I get the timing, and the apparently rushed nature of the City referral, but even so. Maybe I am giving the PL too much credit and they really are that stupid.
Personally, I think the whole thing is an inevitable consequence of how the investigation was started, and how the club has handled the process to a situation it is happy with.