I agree with what Scribbler said. Despite giving outstanding care and having beautiful facilities, many boarding barns aren’t set up management/staffing-wise to accommodate the needs of PPID/IR horses. Things that are simple for a horse in your back yard like soaking feed can be trickier efficiency-wise at a big farm with certain ways of feeding. In my experience, a smaller barn can sometimes be more flexible with feeds and medications. Barns with a dedicated farm manager are a good option for horses who need special care, in my experience.
You’re not alone. My horse absolutely always thrived on pasture and I sought pasture/turnout out as a priority for him as a boarder. Then we got the PPID/IR diagnosis when he turned 25 and his entire care schedule had to be dramatically changed (dry lot, tested hay, etc). I thought we would have to move. I’m forever grateful to my current farm, where he’s getting individualized care and thoughtful management. He’s on tested hay and the farm stores and feeds it. He’s also on a different feed brand from the rest of the farm and he gets soaked hay cubes. I don’t think we could have made all the changes he needed if I boarded at a large facility. I’ve asked for far more than I planned as a boarder, but I got lucky with such a great farm. I try my best to be a respectful boarder by doing things like 1) finding tested hay that can be fed dry so they don’t have to soak 2) never running out of supplies 3) keeping everything simple and organized.
I also happened to move closer to my horse not long before the PPID/IR diagnosis so I was WAY better equipped to handle frequent barn trips. I lived 45+ minutes away for many years because work was in one place and the best barns for him were in a different place. I know that’s not always feasible, but relocating was a huge game changer in my case.
Simple and organized is definitely best when you’re supplying and measuring out feed/meds, as it sounds like you’re already doing.
ETA: For some farms, it’s no big deal to soak a meal, stall a horse separately for feeding, feed a different brand of feed, swap a paddock. But for some, any of those options aren’t feasible through no fault of theirs.