Renewing my Tier 2 Visa - "Extend" or "Update"?

[a_bllk]

I’ve got a question regarding renewing my Tier 2 Skilled Worker Visa.

I am still working for the same company who sponsored my first SWV, however when I applied for the first time my occupation code was 2126 - Design and Development Engineer. Now I need to renew my visa and I see that code is now for Aerospace Engineers (which I’m not), so my new COS should be under 2122 - Mechanical Engineers. Which confuses me about whether to apply to “Extend” or to “Update”.

The UKVI requirements to extend says “Your job is in the same occupation code as when you were given your previous permission to enter or stay in the UK”.

Whereas for updates it says “If you’ll be doing a different job for your current employer, you only need to apply to update your visa if your new job is in a different occupation code.” - Which I am guessing is the right option but I am a bit confused since it is technically the same job, but under a different occupation code this time. What do you think?

Also the route defined on my new CoS is “Skilled Worker (Extensions - ISC Liable)” - is this valid for update applications as well?