After briefly looking over this forum, it doesn't seem like anyone else has suggested this which is surprising because this has been bothering me for quite a while and I'm only just now getting around to making a post on it. The Gen 7 games introduced something called hyper training which allows you to improve the IVs of your pokemon by exchanging bottle caps. Hidden power typing is determined by IVs but it is determined prior to hyper training and the hidden power type stays the same even if you then go and hyper train that pokemon to perfect 31 IVs in every stat. The relevance of this as far as Showdown is concerned is that you no longer have to intentionally decrease the IVs and consequently the stats of your pokemon just to get a certain hidden power type. A good example of why this is actually very important is hidden power fire, one of the most common and useful hidden power typings. If you want to use a hidden power fire Latios in Gen 6, you lose an IV in speed (and also att and sp att) which means you can no longer speed tie with opposing Latios or other base 110s. The trade off for using hidden power fire here is pretty significant, but with the addition of hyper training you can use this hidden power on a 31 speed IV Latios in Gen 7 or anything after like National Dex. The teambuilder unfortunately still corrects to the IVs that it thinks you need to have so you will have to manually fix the IVs on your mons when using certain hidden power types. On top of this, you can fix the IVs on your mons but they won't stay fixed because when you open the import/export tab to copy a paste of the team/mon it defaults back to the hidden power IVs. I'll put some image examples of this below. Seems like a pretty easy fix to make that would improve quality of life in the builder.
Above you can see that I fixed the IVs on my hidden power fire Tangrowth. After opening the Import/Export tab to hypothetically paste this into the damage calculator, the builder defaults back to 30 IVs in att, sp att, and speed because it thinks that is needed for the Tangrowth to have hidden power fire. Just a bit frustrating.
Above you can see that I fixed the IVs on my hidden power fire Tangrowth. After opening the Import/Export tab to hypothetically paste this into the damage calculator, the builder defaults back to 30 IVs in att, sp att, and speed because it thinks that is needed for the Tangrowth to have hidden power fire. Just a bit frustrating.