This is very accurate. Normally western union will give you notes of 1000 pesos, which is just about manageable in pockets if you're getting a few hundred dollars.

I had one instance where there was only one western union I could use (because of the weekend) and they only had 100 and 200 peso notes. I walked out with 300 dollars worth of notes in a black bin bag and hurriedly tried to find a taxi before anyone noticed...