That amount is irrelevant - it’s a good question to ask.
Discussion
If he just wants to learn the process for larger volumes, it is valid in the future. But it is usually a false concern due to having read some unrealistic text on the internet. There is no point in wanting BTC without KYC and every year submitting all the information for income tax and social security.
Yes, for larger volumes and simply general knowledge - he’s a long term holder too so currently no need to submit information every year in the UK until he realises any of it. His concern is precisely about the amounts, too, which are very open to chain analysis. Not everyone likes their “bank statements and transactions” publicly visible and it’s akin to this.
The State already has your bank details, your salary income and other information. It has your expenses in stores, your retirement. Knowing whether or not you bought BTC is the least of your problems. Now, if you need to hide money from the State for some reason, that's another matter, but that case is the exception and most people who worry about KYC don't do that. -- A lot of effort is wasted on something that isn't important to most people. They even put the concern about KYC above BTC, how to store BTC and their own protection.
What is your approach to buying / stacking bitcoin?