result of

pulumi refresh

like below

~ gcp:compute/instance:Instance: (update)
        [id=...]
        [urn=...]
        [provider=...]
        --outputs:--
      - attachedDisks             : [
      -     [0]: {
              - deviceName             : "persistent-disk-1"
              - diskEncryptionKeyRaw   : [secret]
              - diskEncryptionKeySha256: ""
              - kmsKeySelfLink         : ""
              - mode                   : "READ_WRITE"
              - source                 : "<https://www.googleapis.com/compute/v1/projects/xxx/zones/us-central1-c/disks/tuanlq-ocp-home>"
            }
      -     [1]: {
              - deviceName             : "persistent-disk-2"
              - diskEncryptionKeyRaw   : [secret]
              - diskEncryptionKeySha256: ""
              - kmsKeySelfLink         : ""
              - mode                   : "READ_WRITE"
              - source                 : "<https://www.googleapis.com/compute/v1/projects/xxx/zones/us-central1-c/disks/tuanlq-ocp-data>"
            }
      -     [2]: {
              - deviceName             : "persistent-disk-3"
              - diskEncryptionKeyRaw   : [secret]
              - diskEncryptionKeySha256: ""
              - kmsKeySelfLink         : ""
              - mode                   : "READ_WRITE"
              - source                 : "<https://www.googleapis.com/compute/v1/projects/xxx/zones/us-central1-c/disks/tuanlq-ocp-log>"
            }
        ]
      + attachedDisks             : [secret]

I don't know for sure what is happening. but pulumi refresh will check if you have changes made manually in the console as well. so same code might find changes if you did them in the console