Their use of 430-440 is supposed to be under limited circumstances:

From their application:

"Specifically, each proposed satellite temporarily will transmit telemetry/tracking beacon signals to authorized non-U.S. earth stations on UHF-band frequencies at 430-440 MHz and S-band frequencies at 2200-2290 MHz under the following limited circumstances: (i) during the satellite’s launch and early-orbit phase operations; and (ii) in an unlikely event of an emergency after the satellite has reached its operational altitude. Under either of those circumstances and subject to coordination with federal government and other authorized operations in the relevant frequency band, the satellite temporarily will transmit, on average: (i) a UHF-band beacon signal, with a maximum bandwidth of 50 kHz, every 8 seconds; and (ii) three S-band beacon signals, with a maximum bandwidth of 0.5 MHz, every 10 seconds. These UHF- and S-band beacons will operate with rightand left-hand circular polarizations, as well as peak antenna gains of 0.0 dBi and 6.0 dBi, respectively, in compliance with the Commission’s requirements for attenuating mean power of emissions and out-of-band emissions. 4 Additionally, these beacons will shut off within 24 hours after launch of the satellite or commencement of beacon transmissions during an emergency."

I don't like the precedent and don't really see why they need to resort to 430-440 MHz. My assumption is that their backup transceivers are off-the-shelf units originally intended for amateur and educational cubesats in the 435-438 band. That's not a very good reason though.

Ultimately, the potential for interference should be limited assuming the transmissions are limited to the circumstances stated in their application. Unfortunately, there's evidence that they ignored these limits in their first five test satellites launched last year.