I am not a sprinter, or at least I don’t envision myself as one. I do however enjoy sprinting from time to time at the end of my rides. My peak power came after a short easy ride at 1048 watts. Three weeks ago I sprinted at the end of a solo century at .68 IF that had 4000+ feet of climbing and hit 950 watts. Today I hit 986 watts after 56 miles of .73 IF and 5500 feet of climbing.
I feel like my peak wattage should be higher when I am fresh based off these numbers. What gives?
Your peak is your peak, I’m in the 1050-1150 range regardless of freshness so I wouldn’t expect a huge bump in peak power after a short easy ride. What you CAN expect is for something like your 10-20 second power to be higher after less load but our “max” figure is fairly useless on its own and can even be influenced by the power meter much easier than a rolling average
Same reason my Wahoo power is set to show 3 second avg vs instant. At the end of a crit style ride my max is down to 950-1050 but the biggest difference is my sprint power tapers off significantly after a few seconds so if I’m fresh I can hold 1000 for almost 20 seconds even though my peak isn’t much higher, but when I’m tired my power falls very rapidly during those 20 seconds and I’ll be lucky to average 750-800
If the only time you ever sprint is at the end of your rides then that makes sense. You are practicing sprinting tired so you’re good at it. But you don’t sprint fresh so you don’t practice the full muscle fiber activation. Do some rides where you are fresh and do 5-10s sprints with super easy pedaling in between. You’re fresh sprint numbers would likely get better.
I think the predominant energy systems used are quite different for a sprint vs longer ride at that kind of IF. Especially if the long rides were more steady state without any mashing along the way. I know for me at least that the tired legs feeling is pretty different when it comes from sprinting or weight training vs how it feels from a long aerobic ride, but I’m no rocket surgeon.
But are you a brain scientist? 
The difference btw your sprint fresh and sprint after 100mi is nearly 100w (or ~10% higher). That’s fairly large.
You’re not going to spike big sprint watts just because you tried.
Given that you can do 1050 without any specific training, you prob can improve that a decent amount along with raising your peak after 100mi at the same time by having a sprint focused session one a week or every other week.