As executors, my DB and I worked through a checklist of duties and it said to collect all paperwork concerning the deceased person's estate. It didn't mention collecting ALL other paperwork as some of it would have nothing to do with their financial affairs
ALL the paperwork relating to the deceased, not just the financial stuff, is relevant to the estate and it is vital that the Executors collect everything. Perhaps the checklist was not specific enough in this respect.
My comments are based on having been Executor for a few estates, but I am not a lawyer. One estate was a huge challenge as it took several months to track down all of the relevant paperwork.
The easiest one (from a purely admin point of view) was where the deceased had gathered all of the paperwork into a neat file and had included a "Table of Contents" list of assets, bank accounts, ISAs, pensions, name of the solicitor holding the Will etc. and sample copies of recent statements etc. and had written a covering document that included a short "CV" - date of birth, marriage, divorce, re-marriage, husband's death, employers etc - and copies of all the relevant certificates.
Bereavement is hard enough on the families and friends - so my final comment on this thread is to encourage everyone to spend an hour or so on a rainy afternoon to gather as much information as possible, make a list and to put it all into a file (and maybe scan everything onto a PC or memory device) and let your loved ones or Executor know where it is.