Does granting or revoking object privilege make the target table lock exclusively ?

 There are two accounts on target database.

 USER A has schema objects (tables and indexes).
 USER B has privilege to select all of A's table, but way of granting was duplicated.

 B granted object privilege via role and directly with admin option.
 So, I decided to revoke direct privilege.
 
 SQL>  REVOKE SELECT ON A.TABLE_NAME FROM B ;
 
 These SQLs completed with no errors.
 
 But We found some data loading processes behaved unexpectedly.
 It suspended for a few seconds at the same time as revoking privilege from B .
 It accessed using not B but A.

 If it had been arise from my SQL, I suspect them locked tables or dictionaries.