CSV deserialization outputs nothing if there are only a certain number of empty fields

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If CSV input data doesn't satisfy an uncommunicated threshold regarding the number of columns and empty quoted/unquoted fields, CSV deserialization using ConvertFrom-Csv/Import-Csv yields no output. No error/warning is emitted either; the input is effectively ignored.

Steps to reproduce

Test 1

In the following examples, no custom object is emitted by ConvertFrom-Csv irrespective of row count.

# No custom object output, irrespective of row count.

# Example 1a:
@'
"P1"
""
'@ | ConvertFrom-Csv

# Example 1b:
@'
"P1"
""
""
""
'@ | ConvertFrom-Csv

Tests 2-3

In the following examples, a custom object is emitted for all rows except the last.

# Partial custom object output. 
# Output for each row except the last.
# If there is only one row, no object is emitted.

# Example 2a:
@'
"P1","P2"
"",
'@ | ConvertFrom-Csv # Nothing

# Example 2b:
@'
"P1","P2"
"",
"",
'@ | ConvertFrom-Csv # 1 custom object

# Example 3a:
@'
"P1","P2"
,
'@ | ConvertFrom-Csv # Nothing

# Example 3b:
@'
"P1","P2"
,
,
'@ | ConvertFrom-Csv # 1 custom object

Tests 4-6

Custom object output is correct in following examples.

# Custom object output in examples 4-6.

# Example 4a:
@'
"P1","P2"
,""
'@ | ConvertFrom-Csv

# Example 4b:
@'
"P1","P2"
,""
,""
'@ | ConvertFrom-Csv

# Example 5a:
@'
"P1","P2"
"",""
'@ | ConvertFrom-Csv

# Example 5b:
@'
"P1","P2"
"",""
"",""
'@ | ConvertFrom-Csv

# Example 6a:
@'
"P1","P2","P3"
,,
'@ | ConvertFrom-Csv

# Example 6b:
@'
"P1","P2","P3"
,,
,,
'@ | ConvertFrom-Csv

Note:

• As of PS v7.5.0, the CSV data above (examples 1-6) is all generated by ConvertTo-Csv, which may produce quoted ("") or unquoted empty fields by default. See:
  • https://github.com/PowerShell/PowerShell/issues/24699
• How ConvertFrom-Csv interprets unquoted empty fields is also inconsistent. See:
  • https://github.com/PowerShell/PowerShell/issues/17702

Expected behavior

• Test 1: Should emit a custom object with a P1 property.
• Tests 2a & 3a: Should emit a custom object with a P1 and P2 property.
• Tests 2b & 3b: Should emit 2 custom objects, each with a P1 and P2 property.

Actual behavior

• Test 1: No custom object output.
• Tests 2-3: Partial custom object output for all rows except the last.

Environment data

Name                           Value
----                           -----
PSVersion                      7.5.0-rc.1
PSEdition                      Core
GitCommitId                    7.5.0-rc.1
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0