I've had that as well, another part that NEVER fails according to my 30 year mechanic who works mostly on fleet vehicles
Your 30 year mechanic just hasn't happened to see this problem. They routinely fail in any vehicle of any make, GM, Ford, even Toyota, they just make it past warranty so manufacturers don't have to care.
The combined unit saves a little weight and a little cost, and works better than vacuum units when used with turbocharged and diesel engines, so it's going to be the default booster until everything goes electric.
The hydroboost may fail earlier in a PTO van just because it's running whenever the engine is on. If you notice a small fluid leak, the unit can be repaired. Once it gets to spewing oil it needs to be replaced, and don't be tempted to save a couple bucks with a rebuilt. From new they sound like they're ready to fail.