hovermode='x unified' is causing unexpected behavior together with group_by()

library(tidyverse)
library(plotly)

TexasCities_plus_Houston <- ggplot2::txhousing %>% 
  group_by(city) %>%
  plot_ly(x = ~date, y = ~median) %>%
  add_lines(
    name = "Texan Cities", 
    text = ~paste0(city, "\n", median),
    hoverinfo = "text+x"
  ) %>%
  filter(city == "Houston") %>%
  add_lines(name = "Houston")

This works as expected (but the limitation is that it is hard to find Houston city to hover on):
TexasCities_plus_Houston %>% layout(hovermode = "closest")

This solves the above limitation, however, it does not matter which point you hover on, the same city name is shown ("Wichita Falls"). The "median" variable changes as expected, the problem seems to be solely with the variable used in group_by(), in this case, "city".
TexasCities_plus_Houston %>% layout(hovermode = "x unified")

首先使用 plot_ly()、group_by(city)、add_lines() 和 layout(hovermode = "x unified") 运行所提供的 R reproducer。将统一 hover 标签与 hovermode = "closest" 进行比较，并跟踪如何选择分组后的 city 值；完成的标准是统一 hover 显示悬停点所属的 city，同时保留变化的 median。