Is it really necessary to have a lander to perform radio-astronomic observations in moon's shadow? Isn't it easier to have an orbiting spacecraft instead and perform observation while it's orbiting behind the moon?
It's not necessary, but is significantly more radio-quiet than a lunar orbit. And secondly, though unfortunately not something we could really exploit this time, the stable temperatures of the lunar night greatly help with calibration for sensitive measurements like the 21cm Dark Ages signal
Isn’t the benefit here that you don’t have to deal with things such as significant Doppler shift, or having to maintain a supply of propellant for orbit-keeping?
There is perhaps some extra opportunity in a 10-14 day solid observation window, but I don't see why a satellite version couldn't still work in smaller windows.
Another reason could be testing for building a much large radio antenna on the moon's surface in the future which is mentioned to farther down in the article. The moon itself and it's dust has electromagnetic effects that might effect measurements and learning about them now could help future planning.
You'd build an array (see e.g. VLA mentioned in the article or SKA), and it is much easier to combine the data from an array if everything isn't flying around and so there are varying distances between the antennae.
Not for radio telescopes, but how is the current state of optical interference? Would it help if we didn't have to use adaptive optics to compensate for atmospheric turbulence (and have subtly different images at the different telescopes)?
