The testing I did was on Android. Paulius is seeing a similar increase on iOS.

For repro:

I used an ES project and built Il2cpp Android player using the following settings on 2019.1 and 2018.3:

- Old Net 3.x scripting runtime version + Subset api compatibility level + Low/normal stripping
- New Net 4.x runtime + NetStandard20 api compatibility level + low/normal stripping

In both cases, player size increased between the 2018.3 and 2019.1 (Image attached)

I will share the project I used on Owncloud shortly and all the APKs