Retail Heavensward on Steam ARR

[Cooperal]

Now I've been searching for an answer for this specific matter and since I can't find and official word and players can't test it themselves, I'm hoping I can finally get an answer here.

I've already bought a retail and a steam version separately from eachother and have become aware of a couple of scenarios which leave me confused about the state of the seeming one-way compatibility. Here's what I understand so far from reading around:
-A steam purchase of Heavensward cannot be used for a retail copy.
but also
-A retail copy can be used to log on steams trial version as a standard player
but as I also already understand
-A retail copy can't be used to take advantage of steams wallet function

I love the steam platform and would like to play on there, but if I can avoid rendering my retail copy useless I would like to have a go at it. So the question is:

Can the retail copy of Heavensward work on the Steam base game or does the block work both ways?

Or to pitch it differently, is it possible to make a single purchase of Heavensward that won't hinder one version of the base game in favour of the other?

Thank you.

[worldofneil]

-A retail copy can be used to log on steams trial version as a standard player

It's because the installation on the hard disk is exactly the same for Steam and non-Steam versions. The only difference is the serial codes you get and when you use one that you got from Steam (when you buy the game) it flags your account as a "Steam" account when you register it with Square Enix (since they created all the codes they've put some sort of distinction into them), therefore you can only use Steam expansions later.

So to clarify, the Steam trial works with non Steam accounts because you haven't been given a serial code from Steam for the actual game. Likewise (you didn't actually put this in your list), a non-Steam person can log into Steam version of FFXIV and vice versa (I do this all every day), because they're exactly the same install as mentioned above. It is literally just a flag on the account that originates from the serial code used to register the game.

As far as SE have said the block is both ways (obviously we don't actually know it won't work yet, but they're saying it won't so...)

If you're using an account that you bought from Steam, then you have to buy the expansion from Steam and a retail expansion code won't work. Sorry there's just no getting around that apparently as you can't move characters across accounts or get the Steam flag removed from your account.

Short of starting over anyway... sorry for not having a better reply