OG12 CR104 一处选项的语法结构

毛毛的臭脚丫

Increasingly, the stores that have opened in the central shopping district since Colson’s opened have been discount stores.
感觉看不明白这个句子的意思，最后那个have  been  discount  stores。。。这是怎么个结构。。。？

2017

the stores （主语）that have opened in the central shopping district since Colson’s opened （定语从句） have been discount stores. （谓语）

sdcar2010

Increasingly since Colson's opened, other new stores opened have been discount stores.