Soldier drafted from active service to W Class Army Reserve

[CNB]

My great uncle - a special reservist in 1914 - served in 2nd, 3rd and 4th battalions before being transferred to this reserve and then allocated to work in munitions factory.
This was in 1917 and his records show no sign of recent injury to account for this (though he had had problems previously).
Why would they take out an experienced soldier like this? Was it anything to do with him being 'time expired' reservist (joined 1910)? Seems unlikely given conscription.
Any ideas welcome!

[LarsA]

Perhaps this can give a lead? What was his occupation before joining?

Kind regards,
Lars


Class W Reserve and its Territorial Force equivalent Class W(T) were introduced in June 16 by Army Order 203/16. They were ‘for all those soldiers whose services are deemed to be more valuable to the country in civil rather than military employment’. Men in these classes were to receive no emoluments from army funds and were not to wear uniform. They were liable at any time to be recalled to the colours. From the time a man was transferred to Class W, until being recalled to the Colours, he was not subject to military discipline