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It's a fairly convincing argument.
Arguments for a UK find would mainly be lower fees, eliminating currency risk by keeping investments and likely future costs in the same currency.
I wouldn't say either was right or wrong.
Personally I have a mix of UK, developed world ex UK and emerging markets, so three funds that I alternate in. Over the time I've done it (about 12 years) the UK bit has lagged the other two, but I'll carry on doing the same split because the usual reasons.
Here's the reasoning behind investing in an all-world fund instead of just one area or geography i.e. FTSE or S&P or tech: I believe I have no edge over the financial markets.
https://monevator.com/why-a-total-world-equity-index-tracker-is-the-only-index-fund-you-need/