Unusual Behaviour of colon operator : in R - r

Question

2000:2017
The expected output is a vector of the sequence 2000 to 2017 with a step of 1.
Output: 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
'2000':'2017'
However, when I type this command, it still gives me the same output.
Output: 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Unable to understand how it is generating sequence from characters.
Edit 1:
Ultimately, I am trying to understand why the code below worked? How can X2007:X2011 can possibly work? The select function is from dplyr package.
R code
My data also has similar column names as mentioned in the image above but I do not have 'X' there. I just have years like 2007,2008 etc.
For me select(Division, State, 2007:2011) does not work.
Error:Can't subset columns that don't exist.
x Locations 2007, 2008, 2009, 2010, and 2011 don't exist.
But this works select(Division, State, '2007':'2011').

Answer 1

If we check the more generic seq.default, it does changes the type from character to numeric for the from and to
...
if (!missing(from) && !is.finite(if (is.character(from)) from <- as.numeric(from) else from))
stop("'from' must be a finite number")
if (!missing(to) && !is.finite(if (is.character(to)) to <- as.numeric(to) else to))
...
Along on that lines, the documentation of ?: also says so
For other arguments from:to is equivalent to seq(from, to), and generates a sequence from from to to in steps of 1 or -1. Value to will be included if it differs from from by an integer up to a numeric fuzz of about 1e-7. Non-numeric arguments are coerced internally (hence without dispatching methods) to numeric—complex values will have their imaginary parts discarded with a warning.
Regarding the updated question with subset and select, if the column is numeric column name i.e. it starts with digit, it is an non-standard column name and evaluation of those can be done by backquoting
df1 <- data.frame(`2007` = 1:5, `2008` = 6:10,
`2012` = 11:15, v1 = rnorm(5), check.names = FALSE)
subset(df1, select = `2007`:`2012`)
# 2007 2008 2012
#1 1 6 11
#2 2 7 12
#3 3 8 13
#4 4 9 14
#5 5 10 15
Or with dplyr::select
library(dplyr)
select(df1, `2007`:`2012`)
# 2007 2008 2012
#1 1 6 11
#2 2 7 12
#3 3 8 13
#4 4 9 14
#5 5 10 15
If we have X at the beginning (happens when we read the data without check.names = FALSE - by default it is TRUE. Or when we create the dataset with data.frame - here also the check.names = TRUE by default)
df1 <- data.frame(`2007` = 1:5, `2008` = 6:10, `2012` = 11:15, v1 = rnorm(5))
subset(df1, select = X2007:X2012)

Answer 2

From what i know, : tries to coerce its 'arguments' to numeric, so that's why you got that output. Note that "a":"b" gives:
Error in "a":"c" : NA/NaN argument
In addition: Warning messages:
1: NAs introduced by coercion
2: NAs introduced by coercion