If we look deeper into the information in the database, we see that the situation is fairly complex. What follows is a bit of a story, an imaginative interpretation of what may or may not be real patterns in too few games. It is certainly an over simplification because the pro world is constantly competitive with many different ideas being tried all the time. To make sense of all the games presented in the databases is impossible. It is also rather hard to research thoroughly in a reasonable time with the tools available. But enjoy it anyway!
Nevertheless and in broad terms... before we get to '98 we should look back to 1991. Notice the abortive shift from opposite to adjacent that occurred in that year. It looks almost as if White started to change to the adjacent play and then backed off. This is exactly what did happen, but Black was the driver of that change. It was the result of a strategic battle around plays 3 and 4! Around this time Black 3 was most often played at Q3 in the lower right, in preparation for a standard Chinese fuseki, an 'old Kobayashi' enclosure at R5, or a new Kobayashi approach play in the lower left. Against this White played mainly the other star point on the left, so it made little difference whether White played first in the upper or bottom left. However, around 1989-1990 White began playing at C4 instead of D4 on play 4, threatening to play E3 next if Black continued with a Chinese or old Kobayashi. The result was that Black gave up on B4 at Q3! From 1992 through 1995 the most common B4 steadily reverted to the star point in the lower right. This was not a reversion to the earlier interest in playing San-Ren-Sei (except for people like Takemiya). The middle 90’s were an era of Ni-Ren-Sei, where Black typically made an approach move against one of the White star points on the left rather than playing again on the right. Meanwhile as Black shifted away from a heavy emphasis on Q3, interestingly enough White tended to revert to choosing the opposite star point rather than the adjacent one - seemingly without Black playing tit-for-tat and reverting in turn to Q3.
This changed again around 1998. Why? All along, one choice for black on B3 was the play at R4. Through 1996 the reason for playing there was mainly to enclose the lower right with P3 after a White play on the other left side star point. Suddenly in 1997 the most frequently chosen strategy for Black on B5 shifted to an approach in the lower left in order to initiate the mini-Chinese. The following year, the most common choice for B3 was R4 instead of Q4. White reacted immediately by shifting W2 solidly to the adjacent star point in order to preserve flexibility in the choice of W4. We cannot say, "the rest is history", rather it is a story that is still being written.
The years immediately after 1999 saw resurgence in B3 at Q3, as interest in the new Kobayashi created a new, major branch at B5. Although the mini-Chinese was probably the most heavily explored strategy for Black, the combination of the Chinese and the Kobayashi made B3 at Q3 the most frequent beginning to the game. The situation became chaotic in 2002 with the shift to 6.5 point komi. In that year no major fuseki for Black had a winning percentage in the GoGoD database. Nevertheless, Q3 continued as the most frequent choice for B3. This changed finally around 2007 as interest in the Kobayashi has in fact declined. The database reflects the rise and now the fall of the Kobayashi at the professional level - in line with the subject of this thread. The Chinese and variants are back as the principal idea underlying Black’s Q3. Who knows where we will be in ten more years.
