可能是窃听器。或者是故意的我漏掉了什么。
我看了一下GeomPoint$draw_panel。对于pointsGrob，符号的fontsize和lwd被给定/计算为

fontsize = coords$size * .pt + stroke_size * .stroke/2
lwd = coords$stroke * .stroke/2

其中.pt = 2.845276而.stroke = 3.779528。因此，对size和stroke应用了不同的转换，恕我直言，这就是为什么点的大小不会像文档中所述的那样增加到size+stroke，即使对于小的点大小几乎不可见。
这也可以通过将校正因子添加到冲程来“确认”，即通过乘以.pt / .stroke：

dat <- data.frame(
  x = c(.4, .6, .7, .8),
  size = c(10, 20, 0, 10),
  stroke = c(10, 0, 20, 10),
  fill = c("red", "orange", "black", "orange"),
  color = c("blue", "black", "green", "green")
)

library(ggplot2)

p <- ggplot() +
  geom_hline(yintercept = c("Without correction", "With correction"), linewidth = 20) +
  scale_fill_identity(aesthetics = c("fill", "color")) +
  scale_size_identity() +
  scale_x_continuous(limit = c(0.35, 0.85)) +
  theme_void() +
  theme(axis.text.y = element_text())

p +
  geom_point(
    data = dat, mapping = aes(
      x = x, y = "Without correction",
      size = size, stroke = stroke,
      fill = fill, color = color
    ),
    pch = 21
  ) +
  geom_point(
    data = dat, mapping = aes(
      x = x, y =  "With correction",
      size = size, stroke = stroke * .pt / .stroke,
      fill = fill, color = color
    ),
    pch = 21
  )

基于文档中示例的另一个问题示例：

sizes <- expand.grid(size = seq(0, 30, 3) * 2, stroke = seq(0, 30, 3) * 2) |>
  subset(size + stroke == 30)

ggplot(sizes, aes(x = size, size = size)) +
  geom_hline(yintercept = c("Without correction", "With correction"), colour = "white", linewidth = 30) +
  geom_point(aes(y = "Without correction", stroke = stroke), shape = 21, fill = "red") +
  geom_point(aes(y = "With correction", stroke = stroke * .pt / .stroke), shape = 21, fill = "red") +
  scale_x_continuous(expand = c(.1, 0)) +
  scale_size_identity()