I feel the need to point out that I have not experienced any such thing, neither in a one-wing pve with SLF's nor in 1v1 pvp with SLF's on both sides. Is this perhaps outdated?
The only way to find out really is to put it to the test. Two teams fight each other in Open with SLF's in the first round then second round without. And just to complete the scenarios, do another 2 rounds in PG as well.
Mechan's AX group has the same SLF restrictions but they fight in a battlefield with zillions of Thargoid swarms - it's a different environment.
If you can setup the test, let me know and I'll join in and PvP (probably very badly) with the rest of you.
Because I'd like to know for sure as well.