smuggling things past firewalls is trivial. base48 or some other nonsandard scheme or encrypt a zip file and use a bananaphone scheme to make the content look low entropy. No firewall will flag that.
What is bananaphone? Based solely on the video I'm assuming you repeat data over and over again wasting space to obscure the actual type of content.
A lot of inspecting transparent TLS firewalls look for high entropy blocks, the idea being to sniff out encrypted exfiltration. Making them low entropy is straightforward, as you say.