The bug
I was unable to place any block on any side of a redstone ore block with the off-hand, but could do it with the main hand. Tested this several times.
How to reproduce
Place a redstone ore block on the ground
Place a torch in the off-hand, and keep main hand empty
Right-click a side of the redstone ore block
❌ the ore lights up but no torch is placed
Related issues
is duplicated by
Attachments
Comments

I think this is intended. Actually you can't put any block on any side of the redstone ore block with your offhand, because your empty mainhand can always interact with the ore block even if it's already lit (MC-163863). I updated the summary and description to reflect this, hope you will be fine with this.

I doubt this is intentional. The same issue does not affect coal ore.

As opposed to coal ore, redstone ore has a right-click action, so this is very likely to be intentional.

This didn’t happen in 1.14.4. This was probably caused by the fix of MC-161151.
Can confirm in 21w13a.
Can confirm in 21w14a.

Can confirm in 1.17 pre-release 4
Can confirm in 1.18.1.
Can confirm in 1.18.2.
Can confirm in 1.19.
Can confirm in 24w20a. I'd like to request ownership of this report to maintain it by adding future affected versions considering the original reporter has not done so in the past 5 years.

Can confirm in 1.21.4. Relates to MC-165510.