Not really. Those are both very direct answers. The Defiant gets str1 launch bays. Thats not saying that the crew cant find a way to make them str2 but they all come with str1 standard.
Yes and no. Several IN ships, such as Gothic, are actually impossible under RT rules unless they use at least 'Good' Craftsmanship parts, which can alter the item involved's stats including str.
It basically ends up boiling down to was the ship built to a higher or more average standard. BFG is geared toward 'generic' ships as the baseline, but individual forgeworlds have different levels of capability and craftsmanship. And pattern.
That and the difference in the amount of space they take up is bizarrely miniscule, comparatively. Str 1 is 4 units, str 2 is 6, but str 1 holds 3 AC wings, str 2 holds 6. And due to the fact that Defiant only has a single free weapon hard point that cannot accept a broadside weapon, even at str 2 you can pack it with optional components like a sardine can and have room and power to spare. The problem is: at str 1 lbs it can be killed by a single iconoclast very, very easily, particularly compared to the sort of beat down that the Iconoclast would get from every other cruiser.
However, the number of possible arguments for and against is staggering, which is why I'm conceding the point. We'd argue in circles for weeks with the only result of getting irritated with each other.
BTW: I have to throw this out here: I'm a crazy to want a 4 lb Defiant, but it's perfectly OK for Chaos to get the Torpedo Machine known as Schismatic?