All true. And the 'specific properties' you might need might not be cryptographic security. For example, I did some stuff recently in Javascript with procedural

All true. And the 'specific properties' you might need might not be cryptographic security. For example, I did some stuff recently in Javascript with procedural generation that made heavy use of random numbers. I used my own implementation of a mersenne twister, rather than Math.random, precisely so I could have predictable long term and cross-engine repeatability of the random number sequences generated based on the same seed. So how good does the default random number routine in JavaScript really need to be?