Why did he cut half their beards and half their garments?
Malbim citing Mahari: It is because there was a good side to their coming - they said that it was to console him - and a bad side, their intent to spy.
What are "Madveihem"?
Rashi: They are their cloaks. Radak - this is like "Mido Vad" (Vayikra 6:3).
Why does it say "ba'Chetzi"?
Radak: They cut the garments until half, i.e. until the buttocks.
What are "Shesoseihem"?
Rashi: They are their buttocks. Radak - this is like "Chasufai Shes" (Yeshayah 20:4). Yonason translates "until the testicles"; this is the same 1 .
I.e. either way it was cut to the same place, just one explains from the front, and one from the back.