Hi Sandeep,
As per the scenario mentioned above yes this is an intended behavior of crm and you can give write privilege (user level) to enable add existing records to the grid if you want to restrict the user from editing (updating) the record you can write a javascript
to check the security role on load of the entity and disable save functionality.
Regards Make sure to "Vote as Helpful" and "Mark As Answer",if you get answer of your question. Sushant Sarkar Microsoft CRM Dynamics Engineer