As an additional comment to my post on Oct. 30th, I want to add that the search box (top left in the page pane on a PC or the looking glass-Search on mobile (in the kebab menu)) can be used to find anything/everything in your entire document.
Say you have a view of a table with proposals and the table is filtered in such a way that users can only see proposals that have their user name in one of the columns, normally a user might see just a few of all the table rows. Now imagine that the master proposal table is on a hidden page and is filtered in such a way that only the doc owner can see any row in this table and all other users see nothing.
If page locking is in place, general users (editors) can’t change the filters. In the view of the proposal table they only see what is meant for them to see. And even if they stumble upon the hidden page, the only see an empty master table.
Now imagine this user is John, but the table holds proposals for John and Elise. Using the search function and searching for Elise, you will get a hit on the view of the proposals table and you will get a hit on the master table. And even thought these tables are filtered for other users to not see these table rows, through the search function you can not only see, but open a modal to these proposals that were not meant for you to see. If the proposal table holds a sub-table, you will see all the sub tables lines that match this proposal, even if the sub-table is filtered to only give access to the doc owner.
Needless to say: you can search on a persons name, but als on anything else, like an description, an item, a color, etc. The more general your search term, the more hits you will get.
In my opinion: 1) short term - search should be an optional item along with the other optional items in the locking settings and 2) longer term - search should respect table filters (making it the responsibility of the maker to filter sensitive data properly).