Not sure where that quote comes from but "both the Lib Dems and Tig have dismissed talk of any kind of merger" may be technically true but it isnt the whole picture
There has been endless talk about 'arrangements' between the two groups in the press, often coming from Cable himself
Vince Cable: I’ll build a new home for Labour rebels
Last time i looked the impression was definitely agreement about an informal arrangement so they wouldnt stand against each other, and that regular meetings were taking place about a common strategy. From Cables mouth below:
TINGE want to form a 'party' by the autumn (conference season?) and Lib Dems are now going through another moment of change - a new leader will have the choice whether to align more closely with TINGE or not. Cable was broadly supportive - it will be mildly interesting to see what the new leader does about it, if anything. Logic dictates they should form an alliance, but who knows.