Yes, it is possible that things will work ok without copying/re-flashing that, but if the main caldata gets damaged, you might lose wifi completely.
(It would likely be safer to mount the unused part separately like arjendekorte says on that bug).
thanks hnyman for clearing this up 
(also i 100% agree with what you said).
if you still want to go against what they suggest and do it anyways like i did
then here is a build v17.01.1 for wndr3700v4 with luci preinstalled 
you can backup the partitions first like this but when you do move them somewhere else and save them.
dd if=/dev/mtdblock2 of=/tmp/caldata.backup
dd if=/dev/mtdblock10 of=/tmp/caldata_backup.backup
cat diffconfig:
simpy@simpy:~/Build/v17.01.1/source-17.01.1# cat diffconfig
CONFIG_TARGET_ar71xx=y
CONFIG_TARGET_ar71xx_nand=y
CONFIG_TARGET_ar71xx_nand_DEVICE_WNDR3700V4=y
CONFIG_PACKAGE_libiwinfo-lua=y
CONFIG_PACKAGE_liblua=y
CONFIG_PACKAGE_libubus-lua=y
CONFIG_PACKAGE_libuci-lua=y
CONFIG_PACKAGE_lua=y
CONFIG_PACKAGE_luci=y
CONFIG_PACKAGE_luci-app-firewall=y
CONFIG_PACKAGE_luci-base=y
CONFIG_PACKAGE_luci-lib-ip=y
CONFIG_PACKAGE_luci-lib-jsonc=y
CONFIG_PACKAGE_luci-lib-nixio=y
CONFIG_PACKAGE_luci-mod-admin-full=y
CONFIG_PACKAGE_luci-proto-ipv6=y
CONFIG_PACKAGE_luci-proto-ppp=y
CONFIG_PACKAGE_luci-theme-bootstrap=y
CONFIG_PACKAGE_rpcd=y
CONFIG_PACKAGE_uhttpd=y
CONFIG_PACKAGE_uhttpd-mod-ubus=y
patching: ~/Build/v17.01.1/source-17.01.1/target/linux/ar71xx/image/legacy.mk
-wndr4300_mtdlayout=mtdparts=ar934x-nfc:256k(u-boot)ro,256k(u-boot-env)ro,256k(caldata)ro,512k(pot),2048k(language),512k(config),3072k(traffic_meter),2048k(kernel),23552k(ubi),25600k@0x6c0000(firmware),256k(caldata_backup),-(reserved)
+wndr4300_mtdlayout=mtdparts=ar934x-nfc:256k(u-boot)ro,256k(u-boot-env)ro,256k(caldata),512k(pot),2048k(language),512k(config),3072k(traffic_meter),2048k(kernel),120832k(ubi),122880k@0x6c0000(firmware),256k(caldata_backup),-(reserved)
before installing packages from Software tab, make sure your Distribution feeds match this (you dont have to copy/paste, just make sure they show releases/17.01.1) the feeds can be found under luci/admin/system/packages/ipkg
src/gz reboot_core http://downloads.lede-project.org/releases/17.01.1/targets/ar71xx/nand/packages
src/gz reboot_base http://downloads.lede-project.org/releases/17.01.1/packages/mips_24kc/base
src/gz reboot_luci http://downloads.lede-project.org/releases/17.01.1/packages/mips_24kc/luci
src/gz reboot_packages http://downloads.lede-project.org/releases/17.01.1/packages/mips_24kc/packages
src/gz reboot_routing http://downloads.lede-project.org/releases/17.01.1/packages/mips_24kc/routing
src/gz reboot_telephony http://downloads.lede-project.org/releases/17.01.1/packages/mips_24kc/telephony
Link to patched firmware [USE THIS AT YOUR OWN RISK] (I TAKE NO RESPONSIBILIY FOR WHAT YOU DO WITH, OR USE, THESE FILES FOR)
Making this not-clickable, so visiting this link suggests you are willing to take the risk(s) associated with this patched firmware and will not hold me, any one who has posted here, or any of the lede developers accountable for the files held here. https://mega.nz/#F!91tFRKjZ!SQfylZY8_ggUbPZW6Mffgw
if you choose to do so: after you flash, as Mauro Mozzarelli suggests, copy caldata to the new caldata_backup or restore caldata_backup from the partition you saved (i mention this earlier in this post).
if you want to copy caldata to the new caldata_backup location do this:
dd if=/dev/mtdblock2 of=/dev/mtdblock10
Other than that, good day 
Final thanks to hnyman and arjendekorte for their input on this issue. 