I'm pretty darn sure your teacher is mistaken. I just read over the new support documents for Society and Culture and have not seen any limitations for what constitutes a cross cultural component. It didn't seem to affect my mark at all last year when I used generation as a cross cultural component (and my subtitle included the phrase "over time"). You need to incorporate an aspect of continuity/change but this doesn't mean you can't use time/generation (I personally think generation tends to make more sense but I could be biassed) as your main cross cultural component.
The support document does include some examples of cross cultural components, but doesn't limit what you can choose:
"Does the topic reflect some knowledge and understanding of viewpoints different from that of the immediate culture of the student in terms of, for example, socioeconomic group, gender, ethnicity or location?"
(Assessment and Reporting in Society and Culture Stage 6, pg 12)
I know you'll probably want to play it safe and that I'm a random internet stranger
but I'm fairly sure they haven't changed what constitutes a cross cultural component since last year - the board of studies documents don't seem to imply this limitation in the slightest (feel more than free to read over them yourself, in fact I would recommend this so you know what criteria affect the marking scheme of the PIP). Just my two cents.
