This was an active topic of discussion about 2Bronica specificed alkaline or silver oxide for the ETRS, SQ, and GS1 cameras, per their user manuals. Lithium cells did not exist when the bodies were created...even the ETRSi user manual does not list lithium.
Later on, IIRC, Tamron Bronica added lithium only for the ETRS(i) in their website information but not for the SQ and GS1. I do not recall the reason for this. Unfortunately the Tamron information is no longer accessible.today.
There are posts by ETRS owners that the lithium version (PX-28L) worked fine for them.
It is unlikely that you 'damaged' your body simply with Lithium chemistry in the battery...it is simply 6V no matter what chemistry, in that battery form factor!
In further researching, I found this post by someone about the GS-1:
"Bronica (Tamron) recommends against lithium cells for the GS-1 because they keep on functioning at reduced power rather than simply cutting out, resulting in unpredictable results late in the power cycle."
I found a post of mine dated 2010:
"Tamron later said the lithium version of the PX-28 was perfectly fine only for the ETR(Si), but not the SQ or GS. ETR is fine with alkaline, silver oxide, or lithium battery."
The Bronica is essentially an all-mechanical camera, which uses battery power only for light meter power and forSeiko shutter timing circuitry...why the 6V battery chemistry might matter is somewhat puzzling, but the use of 3V lithium cell in an Olympus OM-4 is not endorsed either...for battery lifetime reasons.