draw rate against even opponent in CGOS 9x9

Hi,

This graph is draw rate and black winrate against even opponent in CGOS 9x9.
http://www.yss-aya.com/20200704cgos9x9.png
Blue is black winrate. Red is draw rate.

The higher rating, the higher draw rate.
If it keeps going this way, all the games will be draw in 4500 ELO.
In black winrate, it seems the higher rating, the less than 50%.

There are from 110000 games from 2020-01-01 to 2020-06-30.
For example, draw-rate between programs in their 3300s are 0.444.

   ELO  games  b-win draw w-win black winrate draw-rate
   1800:   32 =( 18/  0/ 14),    0.563,       0.000
   1900:    0 =(  0/  0/  0),    0.000,       0.000
   2000:   62 =( 28/  7/ 27),    0.508,       0.113
   2100:  296 =(132/ 23/141),    0.485,       0.078
   2200:    0 =(  0/  0/  0),    0.000,       0.000
   2300:   33 =( 14/  2/ 17),    0.455,       0.061
   2400:   68 =( 30/  2/ 36),    0.456,       0.029
   2500:  122 =( 54/ 10/ 58),    0.484,       0.082
   2600:  280 =( 98/ 45/137),    0.430,       0.161
   2700:   51 =( 23/  9/ 19),    0.539,       0.176
   2800:  582 =(245/153/184),    0.552,       0.263
   2900: 1458 =(570/433/455),    0.539,       0.297
   3000:  554 =(153/196/205),    0.453,       0.354
   3100:  450 =(116/157/177),    0.432,       0.349
   3200:  131 =( 34/ 52/ 45),    0.458,       0.397
   3300:  124 =( 22/ 55/ 47),    0.399,       0.444
   3400:    0 =(  0/  0/  0),    0.000,       0.000

* GNU GO is 1800 ELO.

Thanks,
Hiroshi Yamashita