1. Why 4+6 is not blitz? 2. Suggestion to add more rapid controls.

4+6 is 8 minutes exactly. So it must be blitz.

Also there is too much default blitz controls (4) and too few rapid (only 1).

I suggest to remove 10+0 and add the following
1. 10+5 ( or 10+3, which is worse but also better than 10+0)

2. 10+15 (or 10+10)

In general there must be 2-3 rapid controls. Extend blitz to full 8 minutes or maybe even to 9.

Rapid starts at 8 minutes, so 8+0 is rapid and so is 4+6

4+6 is not 8 mins. It's 10 mins. Even If it was 8 mins, 8 mins is Rapid so no.

Quick game time controls are based on stats of millions of games. Devs chose the most played time controls. You can always create a custom game.

Exactly 8 is rapid, it should be less than 8 to be blitz.

1. 9 min (maybe more) is considered bli5z at chess.com playchess etc. I dont know why it is truncated here.

2. 8 min and lets say 10+15 are too different controls to evaluate them as one . Best solution would be to extend blitz to full 8 (or 9) minutes.

I just read this:

www.fide.com/fide/handbook.html?id=171&view=article

Appendix A. Rapidplay

A.1
A ‘Rapidplay’ game is one where either all the moves must be completed in a fixed time of more than 10 minutes but less than 60 minutes for each player; or the time allotted plus 60 times any increment is of more than 10 minutes but less than 60 minutes for each player.

Appendix B. Blitz

B.1
A ‘blitz’ game’ is one where all the moves must be completed in a fixed time of 10 minutes or less for each player; or the allotted time plus 60 times any increment is 10 minutes or less.

I don't know why lichess considers 8, 9 and 10 minutos within the rapid category...for me 10 minutes is still blitz

Its absurd how there are 4 default controls per 5 minutes from 3 to 8 min. And 1 control per 17 minutes from 8 to 25.

@Fairplayer1 Because those are the most played controls.