Labour haven't got a leg to stand on here. The average Conservative seat has an electorate of 72,218; the average Labour 68,366. You can argue, as
the Electoral Reform Society blog does, that that doesn't matter too much, or speculate that Labour seats have more people who are
eligible to register, but haven't done so (note that technically, if they were sent a registration form, it's illegal for them not to (it's the same form for registering for jury duty), but it is possible that they themselves never saw the form). But you can't say that evening up the constituency sizes is 'gerrymandering'.
The one bit of possible gerrymandering at present is the small sizes of Welsh constituencies. They have significantly fewer voters than Scotland or England (Scotland has a case for having 3 or 4 seats with fewer electors in, in the Highlands and Islands, because of the physical size of constituencies). Wales ought to have 32 MPs in the current parliament to even up the numbers with England, not 40. And, since
Labour has 26 out of the 40 Welsh MPs, it's Labour who may be benefiting from gerrymandering at the moment.
The plan to add another 50 Tories to the House of Lords is more dubious. But the article skims over that without much thought.