Nope, that is using LGW as an alternate with statistical contingency fuel that is burnt after engine start for whatever reason. Sometimes it is necessary to commit to destination (LHR) in the hold. I wouldn’t say frequently, but it isn’t a rare occasion on the 777. I frequently see remaining fuel figures of 4.0 in the tech log (on the 777) and have landed with similar on more than one occasion last year.
The point I’m trying to make is that different airlines have different fuel policies...comparing Taking PLOG fuel with Saudia is different to taking PLOG fuel with BA, for example. It would be more accurate to compare how many mins of fuel are remaining at shutdown.