I still have problems with this. 

There are threads going back 3 or more years, for example, https://community.tp-link.com/en/home/forum/topic/525212

Why is this feature not implemented!?  My performance on 2.4Ghz still absolutely sucks with any newly released firmware, and it's confirmed by support that this is the issue. Only using some 1.5 year old modded beta do I get reasonable 2.4ghz performance.

Can we expect any of these 'beta' fixes to make it into mainstream anytime in the future? Multiple firrmwares released since, and this forum is full of people who have to use the old beta to get stable performance on 2.4ghz, missing other stability and security fixes. It's just not right!

I do hope something is in the works to address this.