Different pilots treat storm cells differently.. Some will happily fly through, others will want to go round whilst others won't go near them. Whilst the airport is operating close to normal, some pilots spend half an hour being radar vectored over half of southern England. It happens and, rightly so, it is up to the individual crew to take the action they consider necessary on their interpretation of their weather radar.
As a (retired) Heathrow radar controller, given our appalling weather record in the UK, I often experienced thunderstorms on the approaches to Heathrow. Whilst doing my best to direct one or two aircraft into clear skies for 20 minutes, I would land a dozen aircraft who's crews happily flew through the rain. Potent storm cells are often very localised so it was sometimes possible to fly "off-set" approaches one or two miles away from the normal centreline and then turn the aircraft towards the airfield when they entered clear skies.