The decision of 11 March 2020 has just been released here: http://financeandtax.decisions.tribunals.gov.uk//Aspx/view.aspx?id=11590... The Tribunal appeared to find HMRC's guidance of June 2019 on these issues starting here https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm00440 helpful, though they said they were not bound by it. They were dismissed of the earlier archived guidance where HMRC had appeared to link the "grounds" test for SDLT to the way the tests work for capital gains tax.
At para 44 they dismiss the HMRC argument that it is enough for the land to be in common ownership with the dwelling, they said this was a necessary but not sufficient condition for the land to be grounds.
At para 46 is a suggestion that in the absence of evidence of a pattern of commercial use, the fact that the land provided a view for the dwelling would indicate the land counts as the grounds of the dwelling.