Essentially yes. I'm playing an old save from 1.1 on 2.0 with Quality and Elevated Rails enabled but not Space Age. The option still exists to enable Mech Armor for Power Armor Mk4 but it won't work because Space Age isn't loaded.
But there are some mods that enable Mech Armor in the game without the Space Age expansion being loaded like "Mech Armor" by Xorimuth. It would be nice to have Power Armor MK4 be flying mech armor if you have the space_travel_required flag enabled. Players still have to purchase Space Age to get access to those flags.
I did a hacky solution to what I'm asking for, I went into data-updates.lua and edited it from
if settings.startup["pam3-ma2"].value and mods["space-age"] then
local simulations = require("space-age.prototypes.factoriopedia-simulations")
data.raw["armor"]["pamk3-pamk4"].factoriopedia_simulation = simulations.factoriopedia_mech_armor
data.raw["armor"]["pamk3-pamk4"].provides_flight = true
data.raw["armor"]["pamk3-pamk4"].takeoff_sound = {filename = "space-age/sound/entity/mech-armor/mech-armor-takeoff.ogg", volume = 0.2, aggregation = {max_count = 2, remove = true}}
data.raw["armor"]["pamk3-pamk4"].landing_sound = {filename = "space-age/sound/entity/mech-armor/mech-armor-land.ogg", volume = 0.3, aggregation = {max_count = 2, remove = true, count_already_playing = true}}
data.raw["armor"]["pamk3-pamk4"].flight_sound = {sound={filename = "space-age/sound/entity/mech-armor/mech-armor-flight.ogg", volume = 0.2}}
to
if settings.startup["pam3-ma2"].value then
data.raw["armor"]["pamk3-pamk4"].factoriopedia_simulation = simulations.factoriopedia_mech_armor
data.raw["armor"]["pamk3-pamk4"].provides_flight = true
data.raw["armor"]["pamk3-pamk4"].takeoff_sound = {filename = "Power Armor MK3/sound/mech-armor-flight.ogg", volume = 0.2, aggregation = {max_count = 2, remove = true}}
data.raw["armor"]["pamk3-pamk4"].landing_sound = {filename = "Power Armor MK3/sound/mech-armor-land.ogg", volume = 0.3, aggregation = {max_count = 2, remove = true, count_already_playing = true}}
data.raw["armor"]["pamk3-pamk4"].flight_sound = {sound={filename = "Power Armor MK3/sound/mech-armor-flight.ogg", volume = 0.2}}
so, basically I created a "sound" folder and uploaded the sounds from mech armor into that folder and changed the filename for the sounds to reference the sound folder I just created and removed the "space-age" requirement but an official implementation would be to have it see if you have space_travel_required flag.
This way you can have Flying Power Armor MK4 if you have that space_travel_required flag enabled but it doesn't require space-age itself to be loaded. I realize it represents more work to service the few of us that are playing Factorio 2.0 without space-age loaded but space-age purchased.
Sorry if I'm hard to understand, English isn't my first language.