the pyramidon is the only stone in the entire structure that resembles the parent structure. there is a lot of significance about it just like the numerous legends associated with the upper stone of big temple. the pyramids of south and central america, sudan, iran and iraq, china, greece and rome ( yes all three have pyramids) as well as angkor vat and borbudur all have a special spatial significance to them. even in india lingaraja temple, sun temple at konarak all fall into the same category with small variations.
rajaraja deviated from the existing temple shapes for his magnum opus. why is the question?? the original shapes perhaps reverted als why??
that may be due to some traveller coming to chozha naadu during RRC times who has described it.....
say somebody like megasthenes, hieun tsang, fa hien..... and may be we have missed the details of the traveller who had come during RRC times....
Or, karuvur devar (though the existence is disputed by our group members) would have given him the importance of the structure in capturing and retaining cosmic energy....
later people might have wanted to stick to original architecture only and the old style bounced back????