We got ours one at around that age (16) and it was handed down to #2 when they were a similar age.
I was a little disappointed at how little use it got for the first few !in the but I think it being around was great. They would sit on it, spin the wheels, hold the bars and generally get used to being on a bike even if held on to amd pushed around. By the time they were 2 they were both scooting around at adult jogging pace.
I think they’re worth getting as early as possible simply because they won’t depreciate and cam only have a positive effect.
We saw an amazing toy: two bouncy balls under a seat. A cross between a space hipper and balance bike. It looked fantastic but very expensive.
We had / have a Hard bike. The smallest in the range. I was amazed by the balance bikes (value and quality) in Halfords.