relative path with UDIM not working in image Arnold

**Describe the bug**
relative path for a single image with arnold image connected to a standard surface only working when exposed.

relative path for UDIM images with arnold image not working.

**Steps to reproduce**
I'm trying to create a material with arnold standard surface and UDIM images from substance. A material X standard surface with X image for the viewport.

When i use rel path with UDIM, everything works fine for the material X part

but for the arnold images, it only works if i use a single image AND expose the relative filename in material compound attributes.

When I want all UDIM images, it only works if I use absolute path with "".

I'm also having some trouble to understand the "make path relative.." option when loading an image in absolute mode : it seems that it always stays in relative mode (I never have an absolute path in the filename field unless I explicitely paste it).

Last issue which is more a question : is it better in USD with arnold to use tx files or to leave the original exr/png/... files?

**Expected behavior**
relative path should work for Arnold Image, when single image or UDIMs, when exposed or not, absolute or relative path, rel/abs path should be explicit in filename fields...

**Attachments**
If applicable, add screenshots, sample files, etc to help explain your problem.

**Specs (if applicable):**
- Maya version : 2024.2
- mtoa : 5.3.5.2
- Maya USD : 0.27

**Additional context**

I'm trying to create an asset (without bifrost USD) with multiple UDIMs (for a few months...
, enjoying new mayaUSD version bug fixes one after another).

geo exported in arnold usd for render
exported in maya usd for proxy
one file to payload these geo exports and guides, define proxy/render behaviour, also group/component... types
one file for mtl (arnold for render, matX for viewport), one usd file for bindings, then composed with layers in the asset file.

Begin by reproducing the Arnold Image behavior with single-image and UDIM textures on Maya 2024.2, mtoa 5.3.5.2, and Maya USD 0.27; the issue names no source files or tests. Done means relative and absolute paths behave explicitly and consistently for Arnold images, whether the filename is exposed or not, including UDIM paths.

Written by the indexing model from the issue text.