It depends on your pacing strategy…yes, if you raise your FTP and keep your previous power goals, then you exertion level will be lower, likely setting your self up for a better run.
Or, you can keep your original planned IF and get a faster bike split for the same exertion level.
I would say it depends on your confidence in your run.
For me, as a mediocre runner, I used my strength (the bike) to set me up for a good run…while I was never able to pull off a good run in a full IM (long stories…ugh), it worked with great success for multiple 70.3, including punching my ticket (twice) to Chatty Worlds in 2017.
I always rode within myself on the bike (which still often got me a top bike split) and then hit the run relatively fresh.