Do low Korean high school grades still matter for Oxbridge if I apply with achieved A

Hey everyone,
I’m currently studying A-levels through a private online course. Based on assessment data that my tutor has shared publicly, my current performance is roughly tracking at A* in Maths, A* in Further Maths, A* in Economics, and an A in Physics. These aren’t official predicted grades, just an indication of where I stand academically at the moment according to the tutor’s benchmarks and assessments so far.
I have relatively low grades from my Korean high school, and I’m also aware that predicted grades from private online providers aren’t always fully trusted. Because of that, I’m planning to apply using achieved A-level results instead (PQA).
What I’m trying to understand is how much Korean high school grades actually matter for Oxbridge admissions.
If an applicant applies with strong achieved A-levels, a solid personal statement, good academic references, and competitive admissions test scores, can low Korean school grades still be a real deal-breaker for Oxford or Cambridge? Or are they usually treated more as background or contextual information once achieved A-levels are available?
I’d really appreciate any insight, especially from people who applied from non-UK education systems or who are familiar with how Oxbridge admissions works.
Thanks!

Oxford seem to take past grades into account more than cambridge do, so I think it kind of depends. It's definitely possible to get into either with poor grades, maybe just harder for a super competitive course at oxford for example. A-levels, entrance exams and even the personal statement/reference would outweigh those high school grades. Also, I was told by an admissions tutor that they contextualise what country you went to high school (they're easier on chinese/korean students and harsher on US/sub-saharan african students) based on how they view the difficulty of their education system.