1) No, as I've wrote "ctAliasMacAddressTime = The value of sysUpTime when this entry was last modified".
The uptime of the switch is 141 days > then you've done "clear nodealias" > nodealias info is learned again = the value is modified > timestamp of this new learned information is "value of sysUpTime when this entry was last modified" (= ctAliasMacAddressTime).
In my opinion even the CLI only does a calculation of two values to show last learned in date/time format...
last learned = (sysUpTime) - (ctAliasMacAddressTime)
2) ctAliasTimeFilter
Not a MIB expert but if you take a look on that OID it shows "MAX-ACCESS No Access".
If you check other OIDs you'd see that "MAX-ACCESS No Access" doesn't give results - you'd need at least read only = no bug IMHO.
Another thing is the description of this OID = The value of sysUpTime when this entry was last modified.
So even if you are able to query that OID it will give the same "wrong" value if you clear nodealias.
-Ron