Sucks that this will mean an asterisk in your epic run of ETs.
But the FE kills aren't the reason for the special conditions, they are the reason for the no-explosive exclusion within the special condition. IO decided to make an accident-only ET, which is valid. The in-contract story rationale could be that the agency doesn't want any blowback from the chameleon's murder.
But then somebody at IO must have said 'we'll just have a bunch of speedrunners blow him up with FEs', so they added an exclusion to the accident-only rule. So even if that exclusion hadn't been made to counteract FE-runs, your streak would still have ended.