I actually haven't seen this much as an issue at Facebook (I've been an engineer there for a few years). There are some (usually very smart) people who care a lot about systems working reliably, and almost always seem to be a few who are willing to jump on issues like this.
One of the advantages of the "bootcamp" approach outlined in the OP is that people feel empowered to jump from product to product, so if something you care about breaks for a small set of users and you wish to fix it, you can do that. As a few others have pointed out, it doesn't hurt to mention this at review time, and people are often publicly recognized and thanked for these "thankless" efforts.
One of the advantages of the "bootcamp" approach outlined in the OP is that people feel empowered to jump from product to product, so if something you care about breaks for a small set of users and you wish to fix it, you can do that. As a few others have pointed out, it doesn't hurt to mention this at review time, and people are often publicly recognized and thanked for these "thankless" efforts.