Are the eggs in semi-freddo cooked? In the recipe that I used for raspberry semi-freddo, one beats the eggs and castor sugar in a heat-proof dish over simmering water until it becomes thick.
Are the eggs actually cooked? 
What is the purpose of beating it while it is being heated?
It is to create a custard or crème anglaise (I assume there is also cream/milk in the recipe).

If you do not beat the eggs, they will become scrambled eggs.

so the proper cooking term is "tempering" the eggs.

For example: 

http://www.finecooking.com/article/how-to-temper-creme-anglaise