ISIS hostname reflecting suffix re0/re1 on MX Junos which not the case in EVO.
Use of static-host-mapping doesn't help to change the hostname in ISIS database

ISIS database picks the hostname from "set system host-name" stanza.
Whatever hostname is configured under this stanza, same will be picked by ISIS database in Junos.
In Jinos, we generally configure hsotname with suffic re0/re1, however, in EVO, we don't usually configure suffix re0/re1 and system adds it by default and hence the behaviour is different in both.
Static-host-mapping is not to change the host-name in isis database but it is to map hostname & system id hence as per https://www.juniper.net/documentation/us/en/software/junos/is-is/topics/task/junos-software-router-is-system-identifier-configuring.html


Example:


PTX:

JTAC-re0# show | display set | match host-name 
set groups re0 system host-name sparrow
set groups re1 system host-name sparrow

{master}[edit]

JTAC-re0# run show isis database extensive | match host    
    Hostname: sparrow
    Hostname: jtac-MX204-r042-re0

MX:

JTAC-re0# show | display set | match host-name 
set groups re0 system host-name jtac-MX204-r042-re0

[edit]

JTAC-re0# run show isis database extensive | match host 
    Hostname: sparrow
    Hostname: jtac-MX204-r042-re0