PF isn't. Same part number fixture at HD is a COMPLETELY different from a supply house. The HD unit doesn't have a replacment cartridge anywhere on the planet. BTDT...
Really? Do you really think Moen would make two different faucets with the same part number? How would they tell them apart for manufacturing, distribution, and parts if they had the same part number? You would think Moen might be sued if two items with the same part number were built differently internally.
I checked a number of different Moen faucets on homedepot.com and every one of them lists a lifetime warranty. Do you really think Meon isn't going to have the cartridges available if they have a lifetime warranty?
Moen absolutely makes some faucets specifically for big box stores that are not sold at plumbing supply houses. However, the big box faucets have different model names and part numbers. I know for sure the Adler line is only sold at big box stores. A plumber doing work for me couldn't get the Adler faucet I wanted from his supply house and he was told it is only sold at big box stores.
Electronics manufacturers have long made special model numbers for big box stores. They may not be different other than model number, but it keeps customers from price matching since nobody else has the same model number.