Truncate Table locking sys views
Locking for truncate and delete is different. As for locking TRUNCATE behave more like 'ALTER TABLE' than DELETE.  

From Microsoft documentation:
TRUNCATE TABLE (Transact-SQL)
"When the DELETE statement is executed using a row lock, each row in the table is locked for deletion. TRUNCATE TABLE always locks the table (including a schema (SCH-M) lock) and page but not each row".  

As you can see, there is a schema lock on the whole table.