Tower cages round valves any difference ?- on or off...

I read a magazine review somewhere of an integrated valve amp with a well ventilated brass cage per valve and the reviewer said he was yet to try the amp with the protection cages removed from the valves, but stated on previous occasions this brought about an improvement in sound quality - is this 24ct foo? Subliminal, or science...

 

Need to see the amp really and how these towers are fitted.
Valves can be very microphonic so it seems perfectly possible that some sort of protective casing will have some effect.

 

I think there is an improvement (albeit a vanishingly small one) when I have the valve cages on my amp vs off. They're solid though, only ventilated at the top, so I put any effect down to reduction of microphony

 

Could the cages not have an effect on the operating temperature of the valves? I know of one company selling cool dampers which "apparently" reduce the op temp to an optimum level.

Now I've no idea if this works or is complete B.S. but it sounds plausible.