ok well I'll except that for now.
You probably mean 'accept'. "Except" means to exclude.
The photon cloak has been accepted science since the mid-2640s. However, until the Empire of Kilrah premiered the Strakha in 2656 the technology was considered a tactical dead end (and that's looking at this with the eyes of history -- in reality, this was not realized by the Confederation until 2667).
There are two reasons for this. As already stated, the theory behind the photon cloak required it to be 'double blind' - the theoretical cloaked ship (pre-2656) should have been as blind to the outside world as the outside world was to it. Second and probably of equal importance is the fact that energy does not disperse through a cloak field... and generating such a field requires that an exceptional amount of energy be produced. Heat and radiation will build up inside the field and eventually destroy the object if it remains cloaked.
The early Skipper Missiles got around both these problems by simply having the missile periodically decloak to reaquire their targets and vent energy. This wasn't a wildly succesful idea: having your invisible missile dump a massive amount of measurable energy into space during its attack run somewhat betrays the basic concept... and ultimately you simply have an exceptional expensive projectile. If anything, I would argue, the most effective aspect of the early, long-range Skippers was that they could better protect their launch platforms.
The Confederation saw this application of photon cloak technology in action beginning in 2654. My guess would be that the development of the Skipper probably did more to comfort Confederation analysts: they had known that the Empire was experimenting with theoretical photon cloaks for eight years... and what they ultimately encountered in combat was a weapon that very clearly ignored the technical problems rather than dealt with them.
Then we have the Strakha you're referring too, apparently build on a Sartha spaceframe. This weapon is wholly distinct from a photon cloak -- it's a stealth fighter along the lines of the modern F-117 Nighthawk... invisible to sensors but (as the episode makes abundantly clear) targetable by the naked eye. Again, this must have been reassuring to analysts: the Kilrathi had attempted to premiere a stealth fighter that completely abandoned the idea of a photon cloak.
