This sounds like a sufficiently obvious failure mode that I’d be extremely surprised to learn that modern index funds operate this way, unless there’s some worse downside that they would encounter if their stock allocation procedure was changed to not have that discontinuity.
Being an index fund is fundamentally about changing your portfolio when the index changes. There no real way around it if you want to be an index fund.
Being an index fund is fundamentally about changing your portfolio when the index changes. There no real way around it if you want to be an index fund.