I have a theory on this. Perhaps the Dauntless design itself is a known Starfleet design even in Janeways time. As we all know, ships of for example the Galaxy Class had modular bridge designs meaning they may not look the same on all ships even of the same class.
Perhaps the Dauntless used an exterior that was known to Starfleet (and Voyager), through the use of Arturis "Particle syntesis" or whatever method he used. Some aspects of the interior was designed or altered in this manner to make it believeable as a Starfleet vessel, while other sections such as engineering and the bridge were simply "altered" to look like a Starfleet vessel.
Simply put: It's not entirely impossible that Arturis may have gained access to a Starfleet database, either through one of Voyager's shuttles, or while on the Voyager itself. We don't know how his particle syntesis system works or if he was able to "transmit" instructions on how the ship was suppose to be reconfigured, prior to his "discovery" of the lost message from Starfleet. If the ship is suppose to be experimental, and as such been either newly constructed, or retrofitted for experimentation, the Voyager crew wouldn't be completely suspicious of it's design and layout. And if it's a known design by Starfleet, they may have reused it in a later century, much like the reuse of the NX Class --> Akira Class. Perhaps the Dauntless Class of the 24th century was as durable and reliable as the Excelsior/Miranda classes had been during the latter half of the 23rd century, and well into the 24th century.
Real world explanation: Visual effects artists became lazy and sloppy and just through in a bunch of ship designs that looked cool
Topic: Dauntless Class ships, canon? (Read 1728 times)
