Looking at the pictures this thing isn't exactly the typical SFP form factor, it protrudes ~5 cm or so over a normal SFP. So if you swap one of these out it's going to stick out like the proverbial sore thumb.
Who says you can see the side they swapped the optic on? For datacenter cross connect links, its not uncommon for the other side of the link to be somewhere you can't see/have access to.
That's a fair point though in that case someone with physical access can do essentially anything with the cable anyway - this "just" makes it easier.