If the lander is doing 130kts then 15 seconds is just over half a nautical mile. Tightish but not that unusual at a busy airport - for the lander it'd be a later landing clearance than they'd like but on the other hand, larger spacing on final means longer delays in the hold (or extended vectoring or earlier speed reduction), plus a reduced departure rate, all of which costs money and time for the airlines. It's a fairly fine balance.
The absolute, overriding priority is safety and specifically having a plan in case it does all go pear-shaped. As long as a go-around can safely be turned away from a departure it's alright. When you're boxed in by weather or other traffic, though, with limited options, that's a different matter.