At the time, both the recruiter and my new manager explained to me that I should think of the 10% bonus as a baseline expected part of my salary "you will always get this unless you are doing something egregiously wrong". This was indeed what everyone was told, and what management was told to tell people. Of course, this made me recalculate what I thought I was worth and it did in actual fact bring my salary up to roughly market rate.
What the recruiter and my manager said was right. Come bonus time, I and almost everyone else in the company got their bonuses (apart from the people that did egregiously bad, and they saw it coming). In the second year I even qualified for 15% and when I got paid out I really felt that I had actually gotten a bonus. I was banking on 10%, but not 15%! I treated myself to something I'd wanted for ages but could never justify.
Then Covid hit, and suddenly upper upper upper management started signaling that bonuses might not be paid that year. Needless to say, absolutely everyone apart from the CFO was up in arms. Morale, which already wasn't amazing because of Covid, plunged even further and the number of "hallway conversations" increased significantly. People started to leave in larger numbers because the bonus was an expected part of their salary. Each year they waited expectantly to receive it, and if they weren't going to get it this year they would need to go and find a job that paid market rate as base salary. The thing that made this worse was that we were working at one of those few companies that actually did better during Covid. For better or worse, we sold a service that had an increased demand for Covid.
By this time I was a manager, and we were told in a leadership meeting by our head of department where we were all vocally pissed, and were told that we had to pass the message on to the people we managed. Clearly, this is what had happened to him, and to his manager.
The company didn't want to come out and say "you aren't getting bonuses even though we're projected to do better" presumably because it would provide a platform for people to ask why. Instead, they thought it would be better if it came from the direct line manager. Great idea except that we received the message from someone who at the same time said to us "I can't imagine how they'll get away without giving bonuses". It just served to add to the feeling of being cheated.
Anyway, they ended up actually paying the bonuses because the annual revenue figures had increased so much that it was basically impossible for them not to pay them. When we got them, we didn't feel happy that we had received a bonus, we just felt bitter that the company put us through hell for seemingly no reason.
I no longer work at that company.