Creating multiple strata using coords in `make.region`

[erex]

Example in make.population.description shows this:

# Make a multi strata region
poly1 <- data.frame(x = c(0,0,100,100,0), y = c(0,100,100,0,0))
poly2 <- data.frame(x = c(200,200,300,300,200), y = c(10,110,110,10,10))
coords <- list(list(poly1), list(poly2))
region <- make.region(coords = coords)
density <- make.density(region)

When I duplicate this trying to build a two strata study area, I find only one stratum is defined, rather than two

poly1 <- data.frame(x = c(0,0,100,100,0), y = c(0,100,100,0,0))
poly2 <- data.frame(x = c(200,200,300,300,200), y = c(10,110,110,10,10))
coords <- list(list(poly1), list(poly2))
region <- make.region(coords = coords)
plot(region, region.col=c("orange", "purple"))
density <- make.density(region)
pop.desc <- make.population.description(region.obj = region, 
                                        density.obj = density, 
                                        N = c(10,100))
pop <- generate.population(pop.desc, detect = make.detectability(), region)
plot(region)
plot(pop)
num2 <- make.design("line", design.details = c("Parallel", "Systematic"),
                     region.obj = region, design.axis=0, spacing=c(25,50))
mine2 <- make.simulation(single.transect.set = TRUE, design.obj=num2)
t2 <- generate.transects(mine2)
plot(t2)

because both areas are coloured the same (indicating they are from the same stratum) even though make.population.description properly assigns differing numbers of animals to areas. This warning is generated by the call to make.design

Warning: Number of spacing values not equal to number of strata. Using first value only.