Why hEX-S use 64bit arm64 and HEX refresh still use 32bit armv7 , they use same SoC .
I doubt the hEX S refresh will be running 64-bit RouterOS.
The original Youtube video about the hEX refresh, as well as
the original brochure, both talk about "64-bit ARM". But then MikroTik walked that back later. The
current version of the hEX refresh brochure is nearly identical, but they scrubbed all references to "64-bit" from it, and added an "EDIT:" comment to the Youtube video description clarifying it will run in "ARM32 mode".
If you look at the
hEX S refresh brochure, it also doesn't mention "64-bit" anywhere on it. It's only on the main Specifications tab of the product description where it says anything about "64-bit". I have seen MikroTik make mistakes before in the specifications, and I expect that they will update that to remove any reference to "64-bit" from it, to match the regular hEX refresh. This mistake was probably just a hold-over from whatever was going on with the non-"S" model in the early days of putting together its marketing materials, since it's almost certain they were both developed in tandem.
I am having a hard time actually coming up with any concrete information about this SoC. Like the last hEX, it's another MediaTek part, except that it is being marketed under their subsidiary Airoha, who publishes no datasheets on it (at least as far as I can tell, on the publicly accessible part of their site). Since it seems to be a relatively new part, it would be shocking if it were not 64-bit. But both of these I think are the first MediaTek-based products using ARM instruction sets that MikroTik has manufactured, and so perhaps there is some limitation in the SoC that prevents it from being able to run the ROS7 ARMv8 binary code (missing some instructions?), and they aren't willing to make any compromises in how they build the ARM64 package to accommodate those limitations or to build and distribute a second "type" of ARM64 package (admittedly would get confusing), so they opted to just have it run ARMv7 code instead?

Honestly, for a little $60 router, it's hard to argue that it's unreasonable, although I can understand the disappointment...