The important thing here is to consider the use cases.
There are a few things to consider, and I think you've hit on probably the main one, eye tracking, and in your example you've given an example with two fields.
The reason I mention this is that if you have 1000 fields and only one of them is a number, you should consider how important it is to draw attention to this vs a text field.
The reason many spreadsheet tools do this is twofold:
- To indicate the change in formatting
- To allow comparison between rows (Comparing £10 to £1000 is easier if values are right aligned)
The reason this becomes important is that:
a) if there is only numeric entry, or many fields are many are numeric, right alignment allows you to compare inputs.
b) If there is no need yield the benefits of horizontal comparison based on alignment or the majority of entry is text (not number) based the negatives of right alignment and the impact on tracking will likely outweigh that of right aligning numeric values.
A good example of why right align text alignment makes content harder to read is here: https://www.nngroup.com/articles/right-justified-navigation-menus/ but there are equalling compelling arguements for showing right aligned numeric content in tables, so input vs output is important as well as row/field comparison.