If the editor dies during loading, the user obviously fails to complete their edit. If the editor take so long to load that the user quits, the user obviously fails to complete their edit. Excluding such data clearly invalidates the reported data.
Beyond that, it is a normal part of our workflow sometimes open additional wikitext tabs for the purpose of viewing or copying wikitext. This makes the wikitext percentages appear misleadingly low. The our true goal is is increased and sustained contributions by users. The number of tabs they open to while generating those contributions is irrelevant.