Why HMS Tiger became a one-ship class

Why was HMS Tiger a one-ship class, and what might have produced a sister?

She arrived as the Navy shifted from 13.5-inch ships to the Queen Elizabeths; a 15-inch Tiger program could plausibly have produced a sister and near-fast-battleship performance.

Tiger completed the four-ship group of 13.5-inch battlecruisers as the Royal Navy turned to the Queen Elizabeths and their 15-inch guns. The counterfactual changes Australia and New Zealand into 13.5-inch ships, allowing Tiger to become a 15-inch/42-caliber design with a sister. A ship built to Tiger's general standard and capable of 28 knots would, in this interpretation, sit very close to a fast battleship when launched in 1913. The comparison with Hood rests on Tiger's denser subdivision and more extensive armor coverage. Her large barbettes are cited as making a 15-inch design relatively straightforward. The imagined change also involves Beatty choosing the more heavily armed ship as his flagship. That could change signalling within his force, since Tiger's flag captain is imagined correcting faulty instructions and assigning an officer to help Seymour transmit them accurately.