This might need to go in Tri Talk

But I decided to ask on here since it has to do with my training plan. Currently I'm battling plantar fasciitis so running [conventionally, anyway] is out of the question. I'm simply biking and swimming and trying to whip this PF so that I can at least run SOME of the HIM I'm signed up for. Here's where my question comes in:

I'm doing the beginner HIM training plan here on BT - the free one - and I have a question about this week's workout structure. It calls for a rest day tomorrow, speed swim/endurance run Thursday, and "race-specific" swim on Friday. This is a similar structure to last week, except it was a "race-specific" on Thursday and a long day on Friday, both swims. What I'm wondering is if there's any physiological reason for the back-to-back swims? If not I'd probably rather just swim tomorrow, take 'er easy on Thursday and come back fresh for another good swim workout on Friday. I've averaged 9-10 hours of sleep for the past week so I'm definitely well rested [a little anxious to get out and go, really, even at 10:30 PM as I'm typing this!] and last week I felt like I could have structured my training the same way and felt fine.

So: Stick with the plan because it's going to be good for me or adjust for a higher quality Friday swim?