OSHC for Student Visa 500 family - acceptable to split policies?

My partner is applying for a Student Visa (subclass 500) and I'll be listed as a dependent along with our son. My partner is Canadian, and I'm a UK citizen. We're currently sorting out our Overseas Student Health Cover (OSHC) and have received some advice that's making me a bit nervous given how much conflicting info is out there. Our agent suggested that I, as the UK citizen partner, get a separate OSHC policy, while our son is added as a dependent to my partner's OSHC. This setup apparently saves us a huge amount of money, potentially around $10,000, and our agent assured us it's perfectly acceptable from an immigration standpoint. However, I'm worried if splitting the OSHC like this could jeopardize our visa application. Also, I know UK citizens have some reciprocal health arrangements – would I be covered by Medicare anyway, or is OSHC strictly necessary and critical for the visa? And if we do split it, could this cause issues if I ever need to make a claim since I wouldn't be on the main applicant's policy? Any insights would be greatly appreciated!