Blob sasToken blank but build process injecting characters in place of no value?

We've parameterized our sasURI as follows, "https://@{linkedService().StorageAccountName}.blob.core.windows.net/?@{linkedService().StorageSAS}" and changed related lines in our arm-template-parameters-definition.json from:

"sasUri": "|:-sasUri:secureString",
"sasToken": "|",

to

"sasUri": "=",
"sasToken": "-",

The source linked service only has the sasURI populated and the sasToken property is left blank (per the sasToken tool tip in the UI).

The change to the arm-template-parameters-definition.json file is causing our default dynamic value to appear in our parameter file but the build process seems to be appending the blank sasToken as "placeholders".

We're expecting this

"ABlobDyn_RTSAS_properties_typeProperties_sasUri": {
"value": "https://@{linkedService().StorageAccountName}.blob.core.windows.net/?@{linkedService().StorageSAS}"
},

and getting this

"ABlobDyn_RTSAS_properties_typeProperties_sasUri": {
"value": "https://@{linkedService().StorageAccountName}.blob.core.windows.net/?@{linkedService().StorageSAS}?**********"
},

We save in the UI like this:

After you save and edit we now see.....

How can we make the build process not append a blank sas token?

We've tried:

"sasToken": "-",
"sasToken": "",
"sasToken": "=",
and removing "sasToken": entirely.... all produce the same unwanted result.