'meikeerthiya illai poikeerthiya' is an issue that needs to be adressed. Am very much an amateur in this field, anyways let me put forth what I know.
Poets glorifying/deifying the king or any other person of importance is a very normal occurrence all over the world.
Even in PS, we can find two such pieces. One is the place when poets glorify Sundarar and he remarks that he himself is invalid, unable to walk but is being praised so much. This piece is full of wry humour. The next is the famous 'en kavi, en sivi, en pari' quoted by Vandiyath Devan.
Usually this praising was limited to the various poems they sung about the king on various occasions. Meikeerthi did not include these. This raises the question, doesn't a meikeerthi praise the king.
Yes, it does. The king is believed to be an incarnation of Mahavishnu. This holds good for all the kings not only for our beloved RRC who had the sangu, chakra in his hands. Meikeerthi was written was in this viewpoint. The objective being to higlight the achievements of the king and make him revered in the eyes of the common man.
In this process, it is very much possible to spin yarns. But, to knoe whether it was done we need to examine them individually.
For instance, let us take RRC's meikeerthi. The meikeerthi also evolved with the king! All important grants recorded the king's meikeerthi first. The meikeerthi found in the seventeenth year, will not include Irattaipadi ie, Rashtrakutas. Whereas, the meikeerthi found in the ninteenth year will include Irattaipadi, but you cannot find reference to 'munneer pazhantheevu pannirayiram'.
I consider this as the base evidence to state that a meikeerthi was not a poikeerthi. If the king wanted he could have inclued whichever country he wanted. Who is going to question him?
I agree with Swetha. It may be easier to inscribe that 'Sivan appeared in king's dreams and ordered him to build a temple' as there is no way it can be verified. But, the king cannot get inscribed that he gave xx amount of gold to the temple or he beat so-and-so in the war etc. I am sure the kings who built such huge temples would not have behaved like the Kodambakkam Clowns of today who announced relief for the Kumbakonam School Fire Tragedy and promptly forgot about it. My feeling about the kings mentioning their donation is to (1) boost their ego and (2) ensure the continuation of the process/prayer they funded because the public can question the temple authorities if any short cuts are taken (there might have been some even during that time who did not believe in 'sivan soththu kula naasam')
The kalvettus may be a poi keerthi to the extent that it has excluded any mention of war/other atrocities of the king.