@riconeitzel Thank you for your input!
Looks like this table only contains the instructions specific for page configuration files. All other instructions are described in the Layout instructions topic.
(see the text right before the table).
<block> and <argument> are described there, though <arguments> is not.
If you are willing, you can change the PR. But also we can close it, and I will add <arguments> in xml-instructions.md myself.
Please let me know what do you prefer! Thank you.

@almarchenko hi oleksandra, I'm currently slightly out of time. If you get it done in the next 2 weeks, feel free to close the PR and migrate it yourself. If not: Let it open and I'll check back in a week or two. Rico :-)

@riconeitzel
Thank you!
Actually, i've re-read my comment and found that I didn't use the correct formatting, so the names of the instructions were lost%)
It was
"and are described there, though is not."
instead of
" <block> and <argument> are described there, though <arguments> is not."
I wonder what did you think about this strange wording:))
Anyway, thank you for your reply, I will close this and add it quickly myself.