I have absolutely no knowledge of this Heathrow incident, having just arrived back in South Africa. But I did closely follow what happened at Gatwick, not least as I live nearby.
If there is any doubt about safety, an airport authority must take the precautionary option (which does not extend to 36 hours or so without real cause for concern). The aviation industry has a brilliant safety record.
There's a huge different between public perception and actual reality. On the way to Cape Town the other day, we had unusually bad turbulence for about 45 minutes. Surveys show that the majority of people are fearful or concerned when they experience turbulence. Yet the reality is that an average of only 50 passengers per year (and a similar number of cabin crew) are injured out of approximately 2 billion passengers. Fastening your safety belt is the preventative measure in this instance - and there's effectively no danger to the aircraft. If you do what you're asked to do, there's absolutely no reason to feel in any way worried.
Better safe than sorry is a policy that works. I've been held up at Gatwick in a corridor for over an hour after disembarking from a long-haul flight when there was a fire in the airport. We never even smelt the smoke that was elsewhere and we were never in danger (other than breathing in too much body odour from certain passengers) because the fire alert policy worked seamlessly. I've been temporarily inconvenienced by a suspect package bomb scare on two occasions, when there was nothing to actually worry about in either case. But in 1975, I was on a London Underground train when an IRA bomb actually went off. Again, better safe than sorry.