EXIF info in PNG: incorrectly written as zTXt instead of eTXt?

[chemi]

Hi,
According to http://www.exiftool.org/TagNames/PNG.html:
"By default ExifTool writes new string-value tags as as uncompressed tEXt, or compressed zTXt if the Compress (-z) option is used and Compress::Zlib is available."
However, I've tried (exiftool 9.58) and it's written by default as zTXt instead of eTXt:

"exiftool(-k).exe"  -UserComment="hello" foo.png

and what is added:
...zTXtRaw profile type APP1..xœeN[.à .ûç.=B^.8.ëcª4mSïÿ±.mE;#p0‰±{Îïy[Çá»}–õ5»¡.ƒ:ñ!jR.ƒL2.P††hÛ.b®Ü€.$›þèu×Ø. •Aî.¨V,,|Ó«Y.šŠãÝèH±Câ-A.÷©Õáhf`rÌ..kÃù`7*..Eíô©Q.ó¿.:; ·ŸÎø‹á'.=.K'=ŠFõ:Ú².÷..pNÀ¹.P.....IEND®B`,

Am I missing something?
Any way to add it as tEXt?
Thanks.

[chemi]

>>>> eTXt
Sorry: tEXt

[chemi]

I've just noticed a raw profile is added, so this applies?:
"Raw profile information is always created as compressed zTXt if Compress::Zlib is available, or tEXt otherwise."

[chemi]

So the question would be:
Any way to add it as tEXt?

[Phil Harvey]

No.  Currently PNG Raw profiles are always compressed if possible.

I think you probably don't want to be adding EXIF:UserComment to your PNG image.  I would suggest instead PNG:Comment or some XMP tag.

- Phil