Default VPN Apps with OmniROM

I apologize if this post is in the wrong area or off topic. I use an app called TunnelBear for VPN services. Staying hidden as much as possible seems pretty relevant these days. Anyways, it seems rooting and custom roms seems to negatively affect TunnelBear's usefulness. TunnelBear still works for me while using OmniROM, but I was wondering if anyone knows why the TunnelBear Devs claim this conflict. Thank you.
I'm currently using AT&T LG G2 running OmniROM.
Current Device:
AT&T LG G2 OmniROM AOSP Custom Kernel

Retired:
HTC ONE M7 T-MOBILE VARIANT
IMEI UNLOCKED, S-OFF, SUPERCID, ARHD GE 6.1