Lanefan
Victoria Rules
Yes it was, said by he who did said calling-out."Red herrings" was explicitly called out as an intended result.

Exactly. You've got it.The example given was explicitly about confusing the situation with red herrings and extra information so as to force the players to weed through it to find their goal. It was even explicitly said that if they do this weeding in a noticeable way the assassins would be prepared.
Again, exactly; and as intended. They don't have the knowledge they need and thus have to find a way of obtaining it. Doing so will very likely not be easy, nor safe, nor without some frustration and dead ends - and presenting these challenges is the whole point of the scenario.There's no way for the players to make meaningful action resolutions at the start of the presented scenario because there's no information provided to leverage -- anything they try will be a guess first,
And note what I said there: specifically and intentionally included within those challenges is frustration. Impatient players (or players running impatient PCs) aren't likely to do well in this scenario, as it's in part a test of patience and perseverance - a test that I-as-player would probably fail every time, but that's no reason for it not to exist!

If the PCs are careless, or careful but unlucky, then the Assassins will likely be alerted. However if the PCs are careful, or careless but lucky, the Assassins likely won't be alerted. There's also the slight-but-not-zero possibility that the Assassins will be alerted in error, either to the wrong threat or by jumping at shadows.at which point the GM will (especially given the later post of possible details) increase the level of chaff with fully details NPCs that have no reason to be present other than to be a red herring and drive the fiction towards a point the GM can use to justify having the assassins alerted.
Never mind that if the PCs/players realize they've mis-stepped (perhaps something about the Clothier's behaviour or manner clues them in, or they visit the Wit and Wisdom and things don't go smoothly) and potentially alerted the Assassins, the party still has options: for example they can always step back and wait a few days or even weeks for any alerts to die down before trying again; or if time-pressed they can try disguises or hiring locals to gather info; or they can even make themselves obvious and then try laying their own ambush in hopes the Assassins will come to them.
Ah, but here you're making a big assumption: that I-as-DM or I-as-module-writer have a desired outcome in mind.This is an example of using scene setting as GM Force -- Force being using GM authority to drive to a pre-determined or desired outcome regardless of player inputs.
But chances are it doesn't matter much to me* whether they find the guild or not, or what they do with or to it if-when they do.
I'll happily run them through the process looking for it; and if they find it I'll gladly run whatever they decide to do next, be it attack the place or alert the authorities or whatever; and if they decide to turn away and ignore it I'll just as gladly run whatever else they get up to instead.
* - exception: in a written module where the whole point of the adventure is in fact to a) find and b) take down the guild, one hopes there's some what-ifs given by the author should the 'find' process go sideways somehow.