disabled EOIP interface in bridge causes lower MTU

Hi,
I have a very strange issue. Now, i’ve found where the problem was, but I was wondering if it is a RouterOS bug.
Well, I have an EOIP interface set to DISABLED, with MTU = 1458.
Now, I add the interface to a bridge, having MTU = 1500.
The bridge MTU become 1458, even if the port with MTU=1458 is disabled.

Is it a bug or normal behaviour?
Massimo