No DHKey exchange when communicating with device in ncs 2.8.0

[GalBrandwine]

Hey,

We have a library (rust) responcible for communicating with the BLE peripheral Using btmgmt dbus messages to bluez.

We have never initiated a dedicated `aagent` in our gateway.

When communicating with BLE device running ncs 270 - we pass pairing phase, and everything works.

But when communicating with device running ncs 280 - the pairing failed, and communication dropped ungracefully.

In the picture, we see the SMP pairing phase

Left - client communicating with BLE running ncs270 (we can see DHKey exchange)

right - client communicating with BLE running ncs280 (No DHKey exchange, why?)

To make things work I need to manually select a `agent DisplayYesNo`.
1. What was changed between 280 and 270?
2. Why there's no DHKey exchange with v280 when using default-agent?
3. How can I make it work without triggering dedicated agent?

Thanks

[GalBrandwine]

After playing with it more, I have some more information about what is going on
Im failing to pair the device (running ncs280:

I've turned on many DEBUG logs to tyr and understand what is going on on the device:
```
CONFIG_BT_KEYS_LOG_LEVEL_DBG=y
CONFIG_BT_CRYPTO_LOG_LEVEL_DBG=y
CONFIG_BT_SETTINGS_LOG_LEVEL_DBG=y
CONFIG_BT_SMP_LOG_LEVEL_DBG=y
CONFIG_BT_SECURITY_ERR_TO_STR=y
CONFIG_BT_SMP_ERR_TO_STR=y
```

when trying to pair, heres the logs from the BLE device:
```
D: F4:26:79:20:76:A9 (public)
D: Encoded path bt/sc/f426792076a90
I: halo_char_ccc_cfg_write: value=1
I: ****************** TRAP:retry_counter = 0
I: send_trap: trap was sent, payload_size = 24
D: F4:26:79:20:76:A9 (public)
D: Received SMP code 0x01 len 6
D: req: io_capability 0x03, oob_flag 0x00, auth_req 0x29, max_key_size 0x10, init_key_dist 0x0D, resp_key_dist 0x0F
D: F4:26:79:20:76:A9 (public)
D: prnd 5730925b34c1387349d104f1de30d6e5
D: rsp: io_capability 0x03, oob_flag 0x00, auth_req 0x09, max_key_size 0x10, init_key_dist 0x00, resp_key_dist 0x00
D: Received SMP code 0x0c len 64
D:
D: u bc00ca97f3772734a904d3c4c4cf83d1d3c3d11cb548e9498af346484cec4480
D: v 15ffd52949209f9a27f9316c7a6eff235717b5c19bd4aa3ce48c18f522252555
D: x 5730925b34c1387349d104f1de30d6e5 z 0x0
D: res d1573ffdf6d5a1293b3ab3bd5851344e
D: 0x2000e5ad
D: Received SMP code 0x04 len 16
D:
D: Received SMP code 0x05 len 1
E: pairing failed (peer reason 0xc)
D: got status 0xc
D: chan 0x200032dc conn 0x20003078 handle 41 encrypt 0x00 hci status 0x05
E: le_security_changed err = 1
W: Pairing failed conn: F4:26:79:20:76:A9 (public), reason 1

D: chan 0x200032dc cid 0x0006
D: F4:26:79:20:76:A9 (public)
D: F4:26:79:20:76:A9 (public)
D: F4:26:79:20:76:A9 (public)
D: F4:26:79:20:76:A9 (public)
I: con_event log: naks 70, crc ok 0, crc err 0,timeouts 1, events 66, Rssi 0
I: Disconnected (reason 0x16), connection duration: 2972
```

From looking at wiresharks loggings, I asked for a `No Input, No Output` binding.
```Bluetooth Security Manager Protocol
Opcode: Pairing Request (0x01)
IO Capability: No Input, No Output (0x03)
OOB Data Flags: OOB Auth. Data Not Present (0x00)
AuthReq: 0x29, Secure Connection Flag, Bonding Flags: Bonding
001. .... = Reserved: 0x1
...0 .... = Keypress Flag: False
.... 1... = Secure Connection Flag: True
.... .0.. = MITM Flag: False
.... ..01 = Bonding Flags: Bonding (0x1)
Max Encryption Key Size: 16
Initiator Key Distribution: 0x0d, Link Key, Signature Key (CSRK), Encryption Key (LTK)
Responder Key Distribution: 0x0f, Link Key, Signature Key (CSRK), Id Key (IRK), Encryption Key (LTK)
```

According to [Nordics tutorials](academy.nordicsemi.com/.../) it suppose to initiate **JUST WORKS** pairing.
But According int wireshark logs I see:
```
Bluetooth Security Manager Protocol
Opcode: Pairing Failed (0x05)
Reason: Numeric Comparison Failed (0x0c)
```

MY question is:
why does the device expect `Numerical comparison` pairing?