MERGE with DELETE on target with partial match on source?, Sql Server

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create table FooBar (
   fooId int not null,
   barId int not null,
   status varchar(20) not null,
   lastModified datetime not null default sysutcdatetime()
);

insert into foobar (fooid, barid, status) values
 (1, 1, 'ACTIVE') ,(2, 1, 'ACTIVE') ,(1, 3, 'INACTIVE') ,(2, 2, 'INACTIVE')

create table src (
   fooId int not null,
   barId int not null,
   status varchar(20) not null,
   lastModified datetime not null default sysutcdatetime()
);

insert into src (fooid, barid, status)  values
 (1, 1, 'ACTIVE' ) ,(2, 1, 'ACTIVE' ) ,(1, 2, 'INACTIVE') ,(2, 2, 'INACTIVE')

-- t = Target = Destination Table = Mirror from Source
    -- s = Source = New Data source to merge into Target table 
    
    declare @FooId int = 1;
    
    ;with t as (
      select fooId, barId, [status], lastModified 
      from dbo.FooBar f 
      where f.fooId = @FooId
      )
    ,  s as (
      select fooId, barId, [status], lastModified=sysutcdatetime() 
      from src 
      where src.fooId = @FooId
      )
    merge into t 
    using s 
      on (s.FooId = t.FooId and s.barId = t.barId)

/* If the records matches, update status and lastModified. */
        when matched 
          then update set t.[status] = s.[status], t.lastModified = s.lastModified
       
        /* If not matched in table, insert the record */
        when not matched by target
          then insert (fooId,   barId,   [status],  lastModified)
            values (s.fooId, s.barId, s.[status], s.lastModified)
       
        /* If not matched by source, delete the record*/
        when not matched by source
          then delete
     output $action, inserted.*, deleted.*;

View schema
Execution time: 0,05 sec, rows selected: 1, rows affected: 11, absolute service time: 0,19 sec