Cloaking has rarely been perfect, at times it seem that distant cloaked vessels are easier to detect.
The closer it gets, the harder it is to "see."
In both world wars when Germany invaded France, instead of crossing the common border, the germans entered France through a neutral country. That's where the French border was least protected.
To the Dominion, perhaps. The Federation bar exceptional circumstances has not been able to ever detect cloaking technology.