Homogeneity of grounding and groundless presentism

The Grounding Homogeneity Thesis (GHT) is not a precise claim, but a guiding principle that, ceteris paribus, we should prefer philosophical theories on which pairs of statements that have similar logical form have similar kinds of truth grounds or else resemble each other in not having truth grounds. For instance a piece-meal metaethical theory on which what makes stealing be wrong is that it violates the categorical imperative while the fact that murder is wrong has no truth grounds at all violates GHT.

Groundless Presentism is Trenton Merrick's theory on which claims about the past and the future are just true, and there is nothing to make them true. Crisp argues against Groundless Presentism basically on the following grounds. It is now 9:25 am. Then the following two statements are true:

1. Pruss is (tenseless) writing a blog post at 9:25 am.
2. Pruss is (tenseless) writing a blog post at 9:20 am.

But on Groundless Presentism, (2) has no truth grounds, while (1) has truth grounds—my present writing. Yet (1) and (2) seem to have the same logical form.

Question: Can the Groundless Presentist just deny the apparent similarity of logical form? If so, then she is committed to the view that one can't read logical form off the words—one may need to know when a statement is being uttered, for instance. I actually agree, but it is a controversial view.