Soft launch control with boost

Hello everyone

I am wondering - how launch control works, when there's only soft rev limiter(like in fsi engines) but it still builds boost? It's weird, because usually building boost comes with hard ignition retarding, which comes with a lot of pops and bags, like antilag. But, somehow, even with cars without drive-by-wire, it comes with soft rev limiter, keeping revs but also building boost. How is it done? It works kinda like in this video: https://youtu.be/SccjaskA1n8?t=65

this is done in specific launch control strategy modes in aftermarket ECU such as Link ecus there is examples in most software help file but the basics is using a set launch rpm limit (example 5500rpm to control rpm) while full throttle and retarding the ignition timing and fueling to suit.

Regards Ross