SDK15 paring problem

Hi nordic,

I am using SDK15.0 (NRF52840) to design a watch producation which needs pairing. I have a problem that if NRF52840 (peripheral ) has been paired with a smartphone (central), and then I remove the bonded deivce on smartphone side and try to connect the NRF52840 device which bond is removed, the smartphone will be rejected to pair (both android and iphone). As I know, the SDK11.0 has no same problem. If we do the samething between NRF52832 (SDK11.0) and smartphone, when reconnect, the users just need to repair them with no problem.

And If I remove the bonds on NRF52840 side (use function delete_bonds()), then the smartphone will successfully repair the NRF52840.

So I have the following questions:

1 Whether can I implement the same experience as SDK11.0 about the above problem?

2 What is the main difference of bond manager between SDK11.0 and SDK15.0 function?

3 I can define the maximum bonds can be stored in SDK11.0, but SDK15.0 seems to have no same feature. Then what is the purpose of the new (SDK15) design?

If any wrong understanding, please kindly  correct me.