Ok... now I'm sure.  If you run the code to generate the test table as we did above and then run the code below, you'll see what I mean.  Details are in the comments.


--===== This is a single column pivot and it works just fine (for a PIVOT).
     -- It produces the expected 80 rows from a million.
 SELECT  Company
        ,YEAR
        ,Q1Amt = amt.[1]
        ,Q2Amt = amt.[2]
        ,Q3Amt = amt.[3]
        ,Q4Amt = amt.[4]
   FROM (SELECT Company,[Year],[Quarter],Amount FROM #SomeTable3) AS src
          PIVOT (SUM(Amount) FOR [Quarter] IN ([1],[2],[3],[4])
        ) amt
  ORDER BY Company, Year
;
--===== This demonstrates that you can't have more in the src query than what the PIVOT will use
     -- which also means that you MUST have a source query for each column to be pivoted.
     -- All we did was add the Quantity column to the "src" aliased derived table and Pivot no
     -- longer works correctly.  Try it and see. And check out the row count.
SELECT Company
        ,YEAR
        ,Q1Amt = amt.[1]
        ,Q2Amt = amt.[2]
        ,Q3Amt = amt.[3]
        ,Q4Amt = amt.[4]
   FROM (SELECT Company,[Year],[Quarter],Amount,Quantity FROM #SomeTable3) AS src
          PIVOT (SUM(Amount) FOR [Quarter] IN ([1],[2],[3],[4])
        ) amt
  ORDER BY Company, Year
;