Synchronizing does not see change in var name due to exluded dir 'var'

I have a Synchronize configuration with the following settings:
Mode: Mirror Files
Sync Options: Delete Files, Preview changes
Comparison criteria: File size

Transfer settings:
Transfer mode: Binary
Filename modification: No change, Replace
Common options: Preserve timestamp, Calc total size

Files masks:
Exclude files: *.do
Exclude directories: .git, var, bin

I've made some changes in the name of a variable in a js file,
so change 'var oldName' in 'var newName'
If I start to synchronize, WinSCP returns the message: 'No differences'.
But there are!
If I change 'var' to 'va' for testing, the difference is detected.
Seems the filter of the exclude dirs is also applied on the text.

Using WinSCP 5.13 build 8172 on Windows 10 (1709)

[quote="PeterO"]
'Seems the filter of the exclude dirs is also applied on the text.'

UPDATE:
Sorry, this was a premature conclusion.
I boiled down the problem to this:
- created a simple text file local/remote with the only text 'test1'.
- change it remote to 'test2'
Synchronize: No difference detected!
As long as the changed text keeps the same length, no difference is detected.

PeterO wrote:

As long as the changed text keeps the same length, no difference is detected.

Sure, as you have configured WinSCP so:

Comparison criteria: File size

Use "Modification time" criteria instead.

That did the trick. Thx.