Every time this pops up I wish that it was merged with the overland cable maps for a global network view. Turns out something like that exists.
Source: have worked on and around submarine cables in Aus
Except that map is rubbish. Sorry, but it is.
Look at the UK for example, apparently "iomart DC4 Leicester" is just off Berkeley Square, London.
Not only is that technically incorrect (Leicester != London), but its hilarious to propose that anyone would build a datacentre in that part of London (its hedge-fund central where rents are three-digits per square foot .... plus there isn't the space anyway to build a datacentre of any sort of meaningful scale).
And the map is just full of such examples.
So yeah, I've grave concerns for the accuracy of that resource.