It would be true if the maximum raw score was 100% and achieved by a child born in august. Then a child born in december could not obtain the maximum standardised score of 141, even with also a raw score of 100%.
In practice, the maximum raw score is generally not 100%. So an august child may be awarded 141 with a raw score of 90%, whilst a december child will need 97% (I am making up numbers).
Here's further explanations about standardised scores from this site:
http://www.elevenplusexams.co.uk/standa ... scores.php
Hope this helps