Making masah on the plaster of the deceased when giving him ghusl

After ghusl was completed, it was discovered that a large plaster was on the buttocks of the deceased. Blood was visible on the plaster.

The Aalim present said the ghusl was done, and there is no need to remove the plaster and wash the area underneath, because if the plaster is removed, blood might come out. So it was left as-is.

When the body was being placed in the grave, it was seen that blood had come out from that area as it soaked that area of the kafn.

Was the ghusl was completed - was the Aalim correct?