Well, the problem is that the tech support might not understand what they are talking about.
If they have access to 3JU4E1uh5Nxy7mVW2k42rrsGqTAz7gC5mb Bitcoin address, they also have access to the same 3JU4E1uh5Nxy7mVW2k42rrsGqTAz7gC5mb LTC address which is absolutely equivalent to the MQgCXuKf2VpPvGmQ8d3NgW7gA9mSB2ejyd address.
See Litecoin P2SH Converter
So, yes, that is their address, but it requires quite some work from their side to access that address based on their BTC seed and the derivation paths they use for the addresses. It is a real pain in the butt to do it even for a single person. It is especially hard in an exchange, where the seed phrase should not be accessible to any single person…
So the big problem is that probably they have no protocol to do it.