it's very easy to join a pool and prove that they are indeed hashing. It is very easy to publish the mining address. It is very easy to let investors know what the hell is going on.
For some benefit of doubt, if their program didn't include the functionality of joining a pool in the first place, it takes some time adjust that. That said I'm not sure whether publicly released programs offer functionality to work with large and expandable ASIC farms off-the-shelf; the last time I looked they seem to be designed for standalone PC's with hashers connected as plug-and-play hardware, not routers / servers that connect to racks of ASICs through LAN.
If they could solo mine, they can mine on a pool in about 1 minute to change the configuration. Actually mining on a pool is MUCH easier to set up than solo mine.