I think, because of his age, any actual service in the 11th Hussars could only have been after the Anglo Boer War and not before, but, I would still be rather circumspect about it, to be quite honest, simply because he had already been wounded and importantly, in my opinion, at least, he had also been discharged unfit, from the SAMIF.
The Corps of Hussars was not an easy option for those at their peak with no issues whatsoever, let alone someone who already had that particular service in South Africa.
Regarding his additional wartime SAMIF service, the Imperial Hospital Corps was raised in Durban on the 2nd of May 1900, you normally joined for a period of six months, again, not an easy option, you had to be passed as fit for service, it paid very well indeed and perhaps he was attracted by the level of pay.
To be quite honest, I'd be rather surprised if he had served in the 11th Hussars, the only evidence I have seen being the CEF paper, which you showed, but, however unlikely to me, it is not impossible, he could have done, although, you could say whatsoever you liked to join the CEF in the Great War, if they behaved in the way the Army did here.
Any service in the British Army would have been difficult to verify, moreover, men were needed and many were keen to join, if he had said that he had actually been shot to ribbons in South Africa and then further discharged from the SAMIF because he was unfit, he might have made enlisting into the Canadian Expeditionary Force rather more difficult for himself.
I did send you the WO128 folio, today at 09.06 GMT, as you requested, however, it was returned immediately by
[email protected] because the address you gave was invalid.